JP4696142B2 - Resonance frequency detection method and resonance frequency detection apparatus - Google Patents

Description

  The invention according to this application relates to a resonance frequency detection method and a resonance frequency detection device for detecting a resonance frequency of a resonance space.

  It may be necessary to detect the resonant frequency of the resonant space. For example, when sound equipment such as a speaker is installed in a hall or gymnasium and a loud sound is emitted from the loudspeaker, the music from the loudspeaker and the resonance frequency of this space (the loud space where the sound equipment is arranged) are reduced. Speech may be difficult to hear. That is, if a loud sound from a speaker contains a lot of resonance frequency components, resonance occurs at the frequency of this component in the loud sound space. The resonance sounds like "won won ..." or "fan fan ...". This resonance sound is not intended to radiate from the speaker, but makes it difficult to hear music and speech from the speaker.

  In order to prevent this, it is preferable to provide a dip filter or the like that detects the resonance frequency in the loudspeaker space and attenuates the component of the resonance frequency in the audio equipment before the speaker. This makes it difficult for resonance to occur in this loudspeaker space, making it easier to hear music and speech from the speaker. In order to determine the frequency characteristic of the dip filter, first, the resonance frequency of the loud space must be detected.

  Conventionally, an operator of a sound facility or a measurer has relied on his / her hearing to distinguish the loud sound and resonance sound of a speaker and determine the resonance frequency.

  However, it takes some skill and experience to determine whether or not the resonance frequency is obtained by such discrimination. In addition, accurate detection of the resonance frequency cannot always be performed if detection is based on such skill and experience.

  Moreover, even a certain level of skill is difficult to hear the resonance frequency and the feedback frequency by hearing. This is because the resonance frequency is a frequency determined by the characteristics of the resonance space, and the feedback frequency is a frequency determined by the configuration of the feedback loop including the electroacoustic system. These have also become obstacles for automatic measurement and automatic adjustment of audio equipment installed in a loudspeaker space.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a resonance frequency detection method and apparatus capable of accurately detecting a resonance frequency without requiring experience or skill. In particular, it is an object of the present invention to provide a resonance frequency detection method and apparatus capable of detecting the resonance frequency separately from the feedback frequency.

  In order to solve the above-described problem, a resonance frequency detection method according to the invention of the present application squeezes a reference frequency signal that lasts for a predetermined time from a speaker arranged in a resonance space, and receives a sound by a microphone arranged in the resonance space. An attenuation characteristic measurement step for measuring an attenuation characteristic of an output signal of the microphone, and a resonance frequency detection method for detecting a resonance frequency of the resonance space based on the attenuation characteristic, wherein the reference frequency signal is specified A sine wave signal of a frequency or a signal having a component within a predetermined frequency width centered on a specific frequency.

  In order to solve the above-described problem, the resonance frequency detection apparatus according to the present invention includes a sound source unit and a measurement unit, and the sound source unit can generate and output a measurement signal. Is a reference frequency signal lasting for a predetermined time, the reference frequency signal is a sine wave signal of a specific frequency or a signal having a component within a predetermined frequency width centered on a specific frequency, and the measuring means is a microphone An output signal can be input, and the measurement unit measures an attenuation characteristic of the output signal of the microphone and detects a resonance frequency based on the attenuation characteristic.

  In order to solve the above-mentioned problem, another resonance frequency detection method according to the present invention provides a reference frequency signal that lasts for a predetermined time from a speaker disposed in the resonance space and a microphone disposed in the resonance space. Resonance for detecting a resonance frequency of the resonance space based on the attenuation characteristic, comprising a step of attenuating the output signal, receiving sound by the microphone, and measuring an attenuation characteristic of the output signal of the microphone In the frequency detection method, the reference frequency signal is a sine wave signal having a specific frequency or a signal having a component within a predetermined frequency width centered on the specific frequency.

  In order to solve the above problem, still another resonance frequency detection apparatus according to the present invention comprises a sound source means, a signal output means, and a measurement means, and the sound source means generates a measurement signal, The measurement signal is a reference frequency signal lasting for a predetermined time, and the reference frequency signal is a sine wave signal of a specific frequency or a signal having a component within a predetermined frequency width centered on a specific frequency, and the signal output means Is capable of inputting the measurement signal from the sound source means and the output signal of the microphone, and the signal output means is capable of outputting the measurement signal and the output signal of the microphone in order to make a loud sound with a speaker. And the measurement means can input the output signal of the microphone, and the measurement means measures the attenuation characteristic of the output signal of the microphone and detects the resonance frequency based on the attenuation characteristic. To.

  In the above method / apparatus, when the attenuation rate obtained from the attenuation characteristic is slower than a predetermined attenuation rate, the specific frequency of the reference frequency signal may be determined as the resonance frequency.

  In order to solve the above-described problem, another resonance frequency detection method according to the present invention includes a reference frequency signal intermittently repeated a plurality of times from a speaker arranged in the resonance space, and the resonance frequency detection method arranged in the resonance space. An attenuation characteristic measuring step of loudening a delayed signal obtained by delaying the output signal of the microphone with a delay time of 0 or more, receiving the sound by the microphone, and measuring the attenuation characteristic of the output signal of the microphone; A resonance frequency detection method for detecting a resonance frequency of the resonance space based on characteristics, wherein the delay time changes in synchronization with intermittent repetition of the reference frequency signal, and the reference frequency signal is specified. A sine wave signal of a frequency or a signal having a component within a predetermined frequency width centered on a specific frequency. The reference frequency signal may be delayed together with the output signal of the microphone and amplified from the speaker, or may be amplified from the speaker without delay.

  In order to solve the above problem, still another resonance frequency detection apparatus according to the present invention comprises a sound source means, a signal output means, and a measurement means, and the sound source means generates a measurement signal, The measurement signal is a reference frequency signal that is intermittently repeated a plurality of times, and the reference frequency signal is a sine wave signal of a specific frequency or a signal having a component within a predetermined frequency width centered on a specific frequency, The signal output means can input the measurement signal from the sound source means and the output signal of the microphone, and the signal output means inputs the measurement signal and the output signal of the microphone with a delay time of 0 or more. The delayed delayed signal can be output for loudspeaking by a speaker, the signal output means changes the delay time in synchronization with intermittent repetition of the reference frequency signal, and the measuring means And can input the output signal of Ikurohon, said measuring means measures an attenuation characteristic of the output signal of the microphone, based on the attenuation characteristics, to detect the resonant frequency. The reference frequency signal may be delayed together with the output signal of the microphone and amplified from the speaker, or may be amplified from the speaker without delay.

  In the above method / apparatus, it is determined whether or not the attenuation characteristic changes due to the change in the delay time, and when it is determined that the attenuation characteristic changes due to the change in the delay time, The specific frequency of the reference frequency signal may not be determined as the resonance frequency.

  In order to solve the above-described problem, another resonance frequency detection method according to the present invention includes a reference frequency signal intermittently repeated a plurality of times from a speaker arranged in the resonance space, and the resonance frequency detection method arranged in the resonance space. A first loudness state in which the microphone output signal is loudened, or a reference frequency signal that is intermittently repeated a plurality of times, and a phase inversion signal obtained by inverting the phase of the microphone output signal disposed in the resonance space A second loudness state that causes the sound to be loudened, a sound receiving by the microphone, and an attenuation characteristic measuring step of measuring the attenuation characteristic of the output signal of the microphone, and the resonance frequency of the resonance space is determined based on the attenuation characteristic. A resonance frequency detection method for detecting, wherein the loudspeak state is changed from the first loudspeak state to the second loudspeaker in synchronization with intermittent repetition of the reference frequency signal. To, or is changed from the second loudspeaker state to said first loudspeaker state, the reference frequency signal is a signal having components at a predetermined frequency within the width around the sine wave signal or a specific frequency of a specific frequency. The reference frequency signal may be phase-inverted together with the output signal of the microphone, and may be amplified from the speaker, or may be output from the speaker without being phase-inverted.

  In order to solve the above problem, still another resonance frequency detection apparatus according to the present invention comprises a sound source means, a signal output means, and a measurement means, and the sound source means generates a measurement signal, The measurement signal is a reference frequency signal that is intermittently repeated a plurality of times, and the reference frequency signal is a sine wave signal of a specific frequency or a signal having a component within a predetermined frequency width centered on a specific frequency, The signal output means can input the measurement signal from the sound source means and the output signal of the microphone, and the signal output means indicates the state of the measurement signal and the output signal of the microphone with a speaker. A first output state for outputting a loud sound, or a second output for outputting the measurement signal and a phase inversion signal obtained by reversing the phase of the output signal of the microphone for the sound to be produced by the speaker. Can be selectively set to a power state, and the state of the signal output means is synchronized with intermittent repetition of the reference frequency signal from the first output state to the second output state, or the The second output state is changed to the first output state, and the measurement means can input the output signal of the microphone, and the measurement means measures the attenuation characteristic of the output signal of the microphone, and the attenuation characteristic Based on the above, the resonance frequency is detected. The reference frequency signal may be phase-inverted together with the output signal of the microphone, and may be amplified from the speaker, or may be output from the speaker without being phase-inverted.

  In the above method, it is determined whether or not the attenuation characteristic changes due to the change of the loudness state, and when it is determined that the attenuation characteristic changes due to the change of the loudness state, the reference frequency The specific frequency of the signal may not be determined as the resonance frequency. In the above apparatus, the measurement unit may determine whether the attenuation characteristic changes due to a change in the state of the signal output unit. If it is determined that the attenuation characteristic changes due to a change in the state of the signal output means, the specific frequency of the reference frequency signal may not be determined as the resonance frequency.

  Further, in the method / apparatus for detecting the resonance frequency based on the above attenuation characteristic, the measurement of the attenuation characteristic may be repeated a plurality of times while changing the specific frequency of the reference frequency signal.

  According to the present invention, it is possible to accurately detect the resonance frequency without requiring experience or skill, and it is possible to appropriately select the frequency to be set as the center frequency of the dip in the dip filter.

  An embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an acoustic system installed in a loudspeaker space (for example, a resonance space where resonance occurs like a concert hall or a gymnasium). This acoustic system includes a sound source device 2, a dip filter 4, an amplifier 12, and a speaker 13. The sound source device 2 may be a performance device such as a CD player for reproducing a music CD, or may be a microphone, for example. In FIG. 1, the sound source device 2 is shown outside the loudspeaker space 40, but the sound source device 2 may be installed in the loudspeaker space 40. For example, the sound source device 2 may be a microphone installed in the loudspeaker space 40. The dip filter 4 is for removing a signal component of a specific frequency from the output signal of the sound source device 2 and sending it to the amplifier 12. The output signal of the dip filter 4 is amplified by the amplifier 12 and transmitted to the speaker 13, and is output from the speaker 13 in the sound expansion space 40.

  When this loudspeaker space 40 has a resonance frequency, if the loudspeaker sound from the speaker 13 contains a large amount of resonance frequency components, resonance occurs in the loudspeaker space 40, making it difficult to hear music and speech from the speaker 13. However, in this acoustic system, when an appropriate frequency characteristic is set for the dip filter 4, resonance in the loudspeaker space 40 can be prevented without impairing the sound quality of the loudspeaker from the speaker 13.

  In the present embodiment, the resonance frequency is detected in the loud sound space 40, and the frequency to be set as the center frequency of the dip in the dip filter 4 is selected from the detected resonance frequencies. A method and apparatus for detecting a resonance frequency in the loudspeaker space 40 will be described with reference to FIGS.

  FIG. 2 is a schematic block diagram of a system Sa for measuring amplitude frequency characteristics in a loudspeaker space (for example, a concert hall or a gymnasium) 40. This system Sa includes a transmitter 11 that is a sound source means for generating a measurement signal, an amplifier 12 that receives a signal emitted from the transmitter 11 and amplifies the power, and a speaker 13 that receives an output signal from the amplifier 12 and amplifies the sound. And a microphone 14 that receives a loud sound emitted from the speaker 13 and a measuring device 15 that receives an output signal of the microphone 14. The microphone 14 may be a sound level meter.

  The speaker 13 and the microphone 14 are disposed in the loudspeaker space 40. The microphone 14 is disposed at a position where it can receive the reflected sound in the loudspeaker space 40 at a sufficiently large level with respect to the direct sound from the speaker 13.

  The transmitter 11 emits a sine wave signal whose frequency changes with time as a measurement signal. That is, the transmitter 11 transmits a sine wave sweep signal. In the sine wave sweep signal, the level of the sine wave is constant at each time point during the frequency sweep.

  The measuring instrument 15 has a bandpass filter whose center frequency changes with time. This band pass filter temporally changes the center frequency corresponding to the temporal change of the frequency of the sine wave sweep signal transmitted from the transmitter 11. Therefore, the measuring instrument 15 can measure the amplitude characteristic of the frequency at that time by detecting the level of the output signal of the microphone 14 through this band pass filter.

  FIG. 3 is a schematic block diagram of a system Sb for measuring the amplitude frequency characteristic in the sound space 40. This system Sb is obtained by adding a path for synthesizing a certain signal to the system Sa of FIG. That is, the system Sb in FIG. 3 includes a transmitter 11 that is a sound source unit that emits a measurement signal, a mixing device 16, an amplifier 12 that receives an output signal of the mixing device 16 and amplifies the power of the signal, A speaker 13 that receives an output signal to make a loud sound, a microphone 14 that receives a loud sound emitted from the speaker 13, and a measuring device 15 that receives the output signal of the microphone 14 are provided.

  The speaker 13 and the microphone 14 are disposed at the same position in the loudspeaker space 40 as in the system Sa of FIG. The transmitter 11, the amplifier 12, the speaker 13, the microphone 14, and the measuring instrument 15 in the system Sb in FIG. 3 are the same as those in the system Sa in FIG.

  The system Sb in FIG. 3 differs from the system Sa in FIG. 2 in that in the system Sa in FIG. 2, the amplifier 12 receives a signal from the transmitter 11, whereas in the system Sb in FIG. Reference numeral 12 denotes that a signal from the mixing device 16 is input. The mixing device 16 in FIG. 3 inputs the measurement signal (sine wave sweep signal) from the transmitter 11 and the output signal of the microphone 14, synthesizes (mixes) these input signals, and generates this synthesized signal (mixing). Signal).

  FIG. 4 is a characteristic diagram schematically showing the amplitude frequency characteristic of the loud space 40 measured by the system Sa of FIG. 2 and the amplitude frequency characteristic of the loud space 40 measured by the system Sb of FIG. In FIG. 4, a curve Ca indicated by a solid line is an amplitude frequency characteristic by the system Sa of FIG. 2, and a curve Cb indicated by a broken line is an amplitude frequency characteristic by the system Sb of FIG.

  Both system Sa in FIG. 2 and system Sb in FIG. 3 measure amplitude values at a number of frequency points. For example, amplitude values are measured at 1/192 octave intervals in the frequency range to be measured. The measured values at multiple points (multiple frequency points) may be represented on the curves Ca and Cb as the amplitude frequency characteristics of the sound space 40 without being smoothed on the frequency axis, or may be expressed on the frequency axis by some method. It may be smoothed and represented on the curves Ca and Cb. There are various smoothing methods at this time, but smoothing may be performed by, for example, moving average. For example, a moving average of 9 points on the frequency axis may be applied to the measurement values of a large number of frequency points. When a smoothed curve Ca is used, it is preferable to use a smoothed curve Cb. In this case, it is further preferable to obtain the curve Cb by the same smoothing method as that for the curve Ca. For example, if the curve Ca is obtained by a moving average of 9 points on the frequency axis, the curve Cb is also preferably obtained by a moving average of 9 points on the frequency axis.

  The amplitude frequency characteristics of the solid curve Ca in FIG. 4 include not only the characteristics of the electroacoustic system by the amplifier 12, the speaker 13, and the microphone 14, but also the resonance characteristics of the sound space 40. The amplitude frequency characteristics of the broken line Cb in FIG. 4 include not only the characteristics of the electroacoustic system by the amplifier 12, the speaker 13, and the microphone 14, but also the resonance characteristics of the loudspeaker space 40. Due to the feedback loop in which the output signal is input to the amplifier 12 and output from the speaker 13, the resonance characteristic of the loud space 40 is more greatly emphasized than the amplitude frequency characteristic of the real curve Ca. Further, the amplitude frequency characteristic of the broken line Cb in FIG. 4 includes a characteristic due to a feedback loop in which the output signal of the microphone 14 is input to the amplifier 12 and output from the speaker 13. From the difference between the two curves (the real curve Ca and the broken curve Cb), it is possible to know the resonance characteristics and the feedback characteristics of the loud space 40.

  The frequency characteristic shown in FIG. 5 is a characteristic obtained by subtracting the characteristic of the actual curve Ca from the characteristic of the broken curve Cb of FIG. In the characteristic curve Db of FIG. 5, the frequencies that show peaks in the positive direction are the frequency f1, the frequency f21, and the frequency f3. The frequency that shows a peak in these positive directions is likely to be a resonance frequency or a feedback frequency. The number of resonance frequencies in the loudspeaker space 40 is not limited to only one, and is often plural. Also, the number of feedback frequencies is not limited to one, and there are many cases where there are a plurality of feedback frequencies. Of the frequencies f1, f21, and f3, one or more frequencies may be resonance frequencies, and one or more frequencies may be feedback frequencies.

  The feedback frequency here is a feedback frequency in the system Sb of FIG. The feedback loop includes an electrical path from the microphone 14 to the speaker 13 and an acoustic path from the speaker 13 to the microphone 14. The microphone 14 is a measurement microphone for measuring the acoustic characteristics of the loudspeaker space 40. Therefore, for example, it is not necessary to set this feedback frequency as a dip frequency in a dip filter in an electroacoustic system that is permanently installed in the sound expansion space 40. Therefore, it is desirable to know which of the frequencies f1, f21, and f3 in FIG. 5 is the resonance frequency. That is, it is desirable that the resonance frequency can be detected separately from the feedback frequency. For this purpose, it is effective to perform measurement by the system Sc shown in FIG.

  FIG. 6 is a schematic block diagram of the systems Sc1 and Sc2 for measuring the amplitude frequency characteristics in the loudspeaker space 40. FIG. 6A shows the system Sc1 and FIG. 6B shows the system Sc2. The systems Sc1 and Sc2 are obtained by adding a delay device 17 to the system Sb of FIG.

  That is, the systems Sc1 and Sc2 in FIG. 6 include a transmitter 11 that is a sound source means for generating a measurement signal, a mixing device 16, an amplifier 12 that amplifies the power of the signal, and a loudspeaker that receives the output signal of the amplifier 12 and amplifies it. 13, a microphone 14 that receives a loud sound emitted from the speaker 13, a measuring device 15 that inputs an output signal of the microphone 14, and a delay device 17.

  The speaker 13 and the microphone 14 are disposed at the same position in the loudspeaker space 40 as in the system Sa of FIG. The transmitter 11, the amplifier 12, the speaker 13, the microphone 14, and the measuring instrument 15 in the systems Sc1 and Sc2 in FIG. 6 are the same as those in the system Sa in FIG. In these respects, the systems Sc1 and Sc2 in FIG. 6 are common to the system Sb in FIG.

  The systems Sc1 and Sc2 in FIG. 6 are different from the system Sb in FIG. 3 in the following points. That is, in the system Sb of FIG. 3, the mixing device 16 inputs the measurement signal (sine wave sweep signal) from the transmitter 11 and the output signal of the microphone 14, and synthesizes (mixes) these input signals. The synthesized signal is sent to the amplifier 12.

  On the other hand, in the system Sc1 of FIG. 6A, the delay device 17 delays the combined signal of the measurement signal (sine wave sweep signal) from the transmitter 11 and the output signal of the microphone 14, Input to amplifier 12.

  Further, in the system Sc2 of FIG. 6B, the mixing device 16 generates a measurement signal (sine wave sweep signal) from the transmitter 11 and a delay signal obtained by delaying the output signal of the microphone 14 by the delay device 17. The input signals are combined (mixed), and the combined signals are sent to the amplifier 12.

  In any system (systems Sc1 and Sc2), the loudspeaker 13 amplifies the measurement signal and the delayed signal obtained by delaying the output signal of the microphone 14 by the delay device 17.

  FIG. 7 is a characteristic diagram schematically showing the amplitude frequency characteristic of the loud space 40 measured by the system Sa of FIG. 2 and the amplitude frequency characteristic of the loud space 40 measured by the system Sc1 or the system Sc2 of FIG. is there. Strictly speaking, the amplitude frequency characteristic measured by the system Sc1 of FIG. 6A and the amplitude frequency characteristic measured by the system Sc2 of FIG. 6B are not the same, but here they are distinguished from each other. I will explain it.

  In FIG. 7, a curve Ca indicated by a solid line is an amplitude frequency characteristic by the system Sa in FIG. 2, and a curve Cc indicated by a broken line is an amplitude frequency characteristic by the systems Sc1 and Sc2 in FIG.

  Similarly to the system Sa of FIG. 2 and the system Sb of FIG. 3, the systems Sc1 and Sc2 of FIG. 6 also measure amplitude values at a number of frequency points. For example, amplitude values are measured at 1/192 octave intervals in the frequency range to be measured. The measured values at multiple points (multiple frequency points) may be represented on the curves Ca and Cc as the amplitude frequency characteristics of the sound space 40 without being smoothed on the frequency axis, or may be expressed on the frequency axis by some method. It may be smoothed and represented in curves Ca and Cc. There are various smoothing methods at this time, but smoothing may be performed by, for example, moving average. For example, a moving average of 9 points on the frequency axis may be applied to the measurement values of a large number of frequency points. When a smoothed curve Ca is used, it is preferable to use a smoothed curve Cc. In this case, it is further preferable to obtain the curve Cc by the same smoothing method as that for the curve Ca.

  As described above, the amplitude frequency characteristic of the solid curve Ca includes not only the characteristics of the electroacoustic system by the amplifier 12, the speaker 13, and the microphone 14, but also the resonance characteristics of the loudspeaker space 40.

  6 includes a feedback loop in which a delay signal obtained by delaying the output signal of the microphone 14 is input to the amplifier 12 and output from the speaker 13. The amplitude frequency characteristics of the broken curve Cc in FIG. 7 not only show the characteristics of the electroacoustic system by the amplifier 12, the speaker 13, and the microphone 14, but also the resonance characteristics of the loudspeaker space 40 are the amplitude frequency of the real curve Ca. It is emphasized more than the characteristics. Further, the amplitude frequency characteristic of the broken line Cc in FIG. 7 includes the characteristic due to the feedback due to the feedback loop in which the delay signal obtained by delaying the output signal of the microphone 14 is input to the amplifier 12 and output from the speaker 13. ing.

  As described above, the broken curve Cc in FIG. 7 is in common with the broken curve Cb in FIG. 4 in that the resonance characteristic of the loud space 40 is greatly emphasized and the characteristic due to feedback is also exhibited. However, since the systems Sc1 and Sc2 of FIG. 6 have the delay device 17, the configuration of the feedback loop of the systems Sc1 and Sc2 of FIG. 6 is not the same as the configuration of the feedback loop of the system Sb of FIG. Therefore, the characteristic due to feedback appearing on the broken line Cc in FIG. 7 is different from the characteristic due to feedback appearing on the broken line Cb in FIG.

  The frequency characteristic shown in FIG. 8 is a characteristic obtained by subtracting the characteristic of the actual curve Ca from the characteristic of the broken curve Cc of FIG. In FIG. 8, the frequencies having peaks in the positive direction are the frequency f1, the frequency f22, and the frequency f3. There is a high possibility that the frequency having a peak in the positive direction is a resonance frequency or a feedback frequency.

  Here, the characteristic shown in FIG. 5 is compared with the characteristic shown in FIG. The frequency characteristic of FIG. 5 shows a peak in the positive direction at frequency f1, frequency f21 and frequency f3, and the frequency characteristic of FIG. 8 shows a peak in the positive direction at frequency f1, frequency f22 and frequency f3. The frequency f1 and the frequency f3 are frequencies having a peak in the positive direction in common in the frequency characteristics of both drawings. The frequency f21 is a frequency that shows a peak in the positive direction only in the frequency characteristics of FIG. The frequency f22 is a frequency that shows a peak in the positive direction only in the frequency characteristics of FIG.

  As described above, the feedback characteristic shown in the broken line Cc in FIG. 7 is different from the feedback characteristic shown in the broken line Cb in FIG. Therefore, it can be considered that the frequency having a peak in the positive direction due to feedback in the frequency characteristic of FIG. 5 is different from the frequency having a peak in the positive direction due to feedback in the frequency characteristic of FIG. .

  On the other hand, the frequency having a peak in the positive direction due to the resonance of the loud space 40 can be considered to appear in both the frequency characteristics of FIG. 5 and the frequency characteristics of FIG.

  From the above, the frequency f1 and the frequency f3 are resonance frequencies of the sound space 40, the frequency f21 is a feedback frequency based on the feedback loop of the system Sb in FIG. 3, and the frequency f22 is the feedback of the systems Sc1 and Sc2 in FIG. It can be thought of as a feedback frequency based on the loop.

  Therefore, for example, in the acoustic system of FIG. 1, the frequency f1 and the frequency f3 may be set as the center frequency of the dip for the dip filter 4.

  In the above example, no delay device is provided in the system Sb of FIG. However, it can be considered that the output signal of the microphone 14 is delayed by 0 second and sent to the mixing device 16. Then, it can be considered that the difference between the system Sb in FIG. 3 and the systems Sc1 and Sc2 in FIG. 6 is a difference in delay time with respect to the output signal of the microphone 14. That is, in both the system Sb of FIG. 3 and the systems Sc1 and Sc2 of FIG. 6, the output signal of the microphone 14 is delayed and then sent to the mixing device 16, but the delay time is shown. 3 can be considered different from the system Sb of FIG. 6 and the systems Sc1 and Sc2 of FIG.

  Furthermore, if the delay device 17 in the systems Sc1 and Sc2 in FIG. 6 is a device that can arbitrarily set a delay time within a predetermined time range, the systems Sc1 and Sc2 in FIG. 6 are used without using the system Sb in FIG. It is possible to detect the resonance frequency separately from the feedback frequency. That is, the measurement in the systems Sc1 and Sc2 in FIG. 6 is performed twice. However, in the two measurements, the delay time set in the delay device 17 must not be the same. For example, the delay time may be 1 msec in the first measurement, and the delay time may be 2 msec in the second measurement. Further, for example, the delay time may be 0 msec in the first measurement, and the delay time may be 1 msec in the second measurement.

  In the systems Sc1 and Sc2 of FIG. 6, when the delay time set in the delay device 17 is changed, the configuration of the feedback loop is also changed. Therefore, as described above, the resonance frequency can be detected separately from the feedback frequency by performing the measurement in the system Sa in FIG. 1 once and performing the measurement in the systems Sc1 and Sc2 in FIG. 6 twice. is there.

  It should be noted that the following method can be used as to how much difference (time difference) is provided in the delay time between the first measurement and the second measurement. That is, a time difference that does not coincide with the period of a frequency (for example, frequency 1) that shows a peak in the positive direction in FIG. 5 is provided.

  For example, assume that 200 Hz is the feedback frequency in the first measurement. In such a case, if the time difference between the delay time in the first measurement and the delay time in the second measurement is 5 ms, which is the period of the 200 Hz sound wave, 200 Hz becomes the feedback frequency in the second measurement. End up. As a result, it is impossible to determine whether 200 Hz is a resonance frequency or a feedback frequency.

  Therefore, after detecting the frequencies that may be resonant frequencies (frequency f1, frequency f21, and frequency f3 in FIG. 5) by the first measurement, whether these frequencies are the resonant frequencies or the feedback frequency by the second measurement. In order to determine whether or not, it is preferable to provide a time difference that does not coincide with the frequency period at least between the delay time in the first measurement and the delay time in the second measurement. For example, a time difference of one quarter of the frequency period may be provided.

  FIG. 9 is a schematic block diagram of the systems Sd1 and Sd2 including the detection devices 201 and 202 as an embodiment of the resonance frequency detection device according to the present invention. FIG. 9A shows the detection device 201 and the system Sd1. FIG. 9B shows the detection device 202 and the system Sd2.

  In the systems Sd1 and Sd2, the detection devices 201 and 202, the amplifier 12 that receives the signals emitted from the detection devices 201 and 202 and amplifies the power, the speaker 13 that receives and outputs the output signal of the amplifier 12, and the speaker 13 radiates. And a microphone 14 for receiving a loud sound. The detection devices 201 and 202 receive the output signal of the microphone 14. The speaker 13 and the microphone 14 are arranged in a loudspeaker space (for example, a concert hall or a gymnasium) 40. The microphone 14 is disposed at a position where it can receive the reflected sound in the loudspeaker space 40 at a sufficiently large level with respect to the direct sound from the speaker 13.

  The detection devices 201 and 202 include a transmission unit 21, a measurement / control unit 25, a mixing unit 26, an opening / closing unit 27, and a delay device 28 of variable delay time type. The transmitting unit 21 functions as a sound source unit that generates a measurement signal. The measurement / control unit 25 functions as a control unit that controls each unit in the detection devices 201 and 202, and also functions as a measurement unit that measures frequency characteristics. The delay device 28 functions as a delay means. The mixing unit 26, the opening / closing unit 27, and the delay device 28 constitute a signal switching unit.

  In the systems Sd 1 and Sd 2, in the detection devices 201 and 202, the measurement / control unit 25 controls the transmission unit 21 to output a measurement signal from the transmission unit 21. This measurement signal is a sine wave signal whose frequency changes with time, that is, a sine wave sweep signal. In the sine wave sweep signal, the level of the sine wave is constant at each time point during the frequency sweep.

  6A, the mixing unit 26 combines (mixes) the signal from the transmission unit 21 and the signal from the opening / closing unit 27, and outputs the combined signal (mixing signal). . The synthesized signal is delayed by the delay device 28, input to the amplifier 12, amplified, input to the speaker 13, and radiated from the speaker 13 to the loud space 40 as a loud sound. The sound in the loudspeaker space 40 is received by the microphone 14, and the output signal of the microphone 14 is input to the detection device 201. In the detection device 201, the output signal of the microphone 14 is branched and sent to the measurement / control unit 25 and the opening / closing unit 27.

  On the other hand, in the detection device 202 of FIG. 6B, the mixing unit 26 synthesizes (mixes) the signal from the transmission unit 21 and the signal from the opening / closing unit 27, and generates the combined signal (mixing signal). Output. The output signal of the mixing unit 26 is amplified by the amplifier 12 and input to the speaker 13, and is radiated from the speaker 13 to the sound space 40 as a sound. Sound in the loudspeaker space 40 is received by the microphone 14, and the output signal of the microphone 14 is input to the detection device 202. In the detection device 202, the output signal of the microphone 14 is branched and sent to the measurement / control unit 25 and the delay device 28. The output signal of the delay device 28 is sent to the opening / closing unit 27.

  In the detection devices 201 and 202, the measurement / control unit 25 has a band-pass filter whose center frequency changes with time. This band pass filter temporally changes the center frequency in response to a temporal change in the frequency of the sine wave sweep signal transmitted by the transmission unit 21. Therefore, the measurement / control unit 25 can measure the amplitude characteristic of the frequency at that time point by detecting the level of the output signal of the microphone 14 through this bandpass filter.

  The measurement / control unit 25 can control the opening / closing of the opening / closing unit 27. Therefore, the open / close unit 27 can be set to the “open” state, and only the measurement signal from the transmitting unit 21 can be amplified from the speaker 13, or the open / close unit 27 can be set to the “closed” state and the measurement from the transmitting unit 21 can be performed. The loudspeaker 13 and the delayed signal of the output signal of the microphone 14 can be amplified.

  Further, the measurement / control unit 25 can set at least two delay times in the delay device 28.

  For example, the delay time of the delay device 28 may be arbitrarily set to either 0 ms or 1 ms, or may be arbitrarily set to either 1 ms or 2 ms. You may be able to do it. Further, it may be arbitrarily set to any one of 0 ms, 1 ms, and 2 ms.

  In the systems Sd1 and Sd2 of FIG. 9, if the opening / closing part 27 is set to the “open” state, the same amplitude frequency characteristic as that measured by the system Sa of FIG. 2 can be measured.

  If the opening / closing part 27 is set to the “closed” state and the delay time of the delay device 28 is set to 0 ms, the same amplitude frequency characteristic as that measured by the system Sb of FIG. 3 can be measured.

  When the opening / closing part 27 is set to the “closed” state and the delay time of the delay device 28 is set to a predetermined time other than 0 (for example, 1 msec), the predetermined time (for example, 1 m) is applied to the delay device 17 of the systems Sc1 and Sc2 in FIG. Amplitude frequency characteristics similar to those measured when setting (second) as the delay time can be measured.

  As described above, the resonance frequency of the sound space 40 can be detected from the amplitude frequency characteristic measured in this manner, separately from the feedback frequency. All the operations for detecting the resonance frequency from the measured amplitude frequency characteristic are performed by the measurement / control unit 25.

  The procedure for detecting the resonance frequency by setting the delay time of the delay device 28 to 0 ms and a predetermined time other than 0 (for example, 1 ms) in the systems Sd1 and Sd2 has been described above. However, in the systems Sd1 and Sd2, the resonance frequency is detected by setting the delay time of the delay device 28 to a first delay time other than 0 (eg, 1 msec) and a second delay time other than 0 (eg, 2 msec). You can also In short, it is only necessary to switch the delay time in two ways. One of these two delay times may be 0 milliseconds, or both may be non-zero times.

  FIG. 10 is a diagram showing an example of a configuration that can be employed as the delay device 28 in the detection devices 201 and 202 of FIG. As the delay device 28 (variable delay time type delay device) of FIG. 9, a delay device 28a as shown in FIG. 10 (a) may be adopted, or a delay device 28b as shown in FIG. 10 (b) is adopted. May be.

  The delay device 28a of FIG. 10A includes a changeover switch 29 and a delay element 50 whose delay time is fixed to a predetermined time other than 0 (for example, 1 msec). By controlling the changeover switch 29, the delay time of the delay device 28a can be switched between 0 msec and the predetermined time (for example, 1 msec).

  The delay device 28b of FIG. 10B includes a delay element 51 that can arbitrarily set the delay time within a predetermined time range. The delay time of the delay element 51 may be controlled to be switched between 0 ms and 1 ms, for example, or may be controlled to be switched between 1 ms and 2 ms, for example.

  The apparatus and method for detecting the resonance frequency separately from the feedback frequency by delaying the output signal of the microphone 14 disposed in the loudspeaker space 40 has been described above.

  Next, an apparatus and method for detecting the resonance frequency separately from the feedback frequency by inverting the phase of the output signal of the microphone 14 disposed in the loudspeaker space 40 will be described.

  FIG. 11 is a schematic block diagram of the systems Se1 and Se2 for measuring the amplitude frequency characteristics in the loud space 40. FIG. 11 (a) shows the system Se1, and FIG. 11 (b) shows the system. Se2 is shown.

  The systems Se1 and Se2 are obtained by adding a phase inverting device 19 to the system Sb of FIG. That is, the systems Se1 and Se2 in FIG. 11 include a transmitter 11 that is a sound source means for generating a measurement signal, a mixing device 16, an amplifier 12 that amplifies the power of the signal, and a loudspeaker that receives the output signal of the amplifier 12 and amplifies the sound. 13, a microphone 14 that receives a loud sound emitted from the speaker 13, a measuring device 15 that inputs an output signal of the microphone 14, and a phase inverting device 19 that inverts and outputs the phase of the input signal.

  The speaker 13 and the microphone 14 are disposed at the same position in the loudspeaker space 40 as in the system Sa of FIG. The transmitter 11, the amplifier 12, the speaker 13, the microphone 14, and the measuring instrument 15 in the systems Se1 and Se2 in FIG. 11 are the same as those in the system Sa in FIG. In these respects, the systems Se1 and Se2 in FIG. 11 are common to the system Sb in FIG.

  The systems Se1 and Se2 in FIG. 11 are different from the system Sb in FIG. 3 in the following points. That is, in the system Sb of FIG. 3, the mixing device 16 inputs the measurement signal (sine wave sweep signal) from the transmitter 11 and the output signal of the microphone 14, and synthesizes (mixes) these input signals. After that, it is sent to the amplifier 12.

  On the other hand, in the system Se1 of FIG. 11A, the mixing device 16 converts the combined signal of the measurement signal (sine wave sweep signal) from the transmitter 11 and the output signal of the microphone 14 into the phase inverting device 19. And the phase is inverted, and then sent to the amplifier 12.

  Further, in the system Se2 of FIG. 11B, the mixing device 16 receives the measurement signal (sine wave sweep signal) from the transmitter 11 and the output signal of the phase inverting device 19 to which the output signal of the microphone 14 is input. The input signals are combined (mixed), and the combined signals are sent to the amplifier 12.

  In any system (system Se1, Se2), the loudspeaker 13 amplifies the measurement signal and the phase inversion signal obtained by inverting the phase of the output signal of the microphone 14.

  FIG. 12 is a characteristic diagram schematically showing the amplitude frequency characteristic of the loud space 40 measured by the system Sa of FIG. 2 and the amplitude frequency characteristic of the loud space 40 measured by the systems Se1 and Se2 of FIG. . Strictly speaking, the amplitude frequency characteristic measured by the system Se1 in FIG. 11A and the amplitude frequency characteristic measured by the system Se2 in FIG. 11B are not the same, but here they are distinguished. I will explain it. In FIG. 12, a curve Ca indicated by a solid line is an amplitude frequency characteristic by the system Sa of FIG. 2, and a curve Ce indicated by a broken line is an amplitude frequency characteristic by the systems Se1 and Se2 of FIG.

  Similarly to the system Sa of FIG. 2 and the system Sb of FIG. 3, the systems Se1 and Se2 of FIG. 11 also measure amplitude values at a number of frequency points. For example, amplitude values are measured at 1/192 octave intervals in the frequency range to be measured. The measured values at multiple points (multiple frequency points) may be represented on the curves Ca and Ce as the amplitude frequency characteristics of the loud space 40 without being smoothed on the frequency axis, or may be expressed on the frequency axis by some method. It may be smoothed and represented on the curves Ca and Ce. There are various smoothing methods at this time, but smoothing may be performed by, for example, moving average. For example, a moving average of 9 points on the frequency axis may be applied to the measurement values of a large number of frequency points. When a smoothed curve Ca is used, it is preferable to use a smoothed curve Ce. In this case, it is further preferable to obtain the curve Ce by the same smoothing method as that for the curve Ca.

  As described above, the amplitude frequency characteristic of the solid curve Ca includes not only the characteristics of the electroacoustic system by the amplifier 12, the speaker 13, and the microphone 14, but also the resonance characteristics of the loudspeaker space 40.

  The system Se1 and Se2 in FIG. 11 includes a feedback loop in which a phase inversion signal of the output signal of the microphone 14 is input to the amplifier 12 and output from the speaker 13. Therefore, the amplitude frequency characteristic of the broken curve Ce in FIG. 12 shows not only the characteristics of the electroacoustic system by the amplifier 12, the speaker 13, and the microphone 14, but also the resonance characteristics of the loudspeaker space 40 of the real curve Ca. It is emphasized more than the amplitude frequency characteristic. Further, the amplitude frequency characteristic of the broken line Ce in FIG. 12 includes the characteristic due to the feedback due to the feedback loop in which the phase inversion signal of the output signal of the microphone 14 is input to the amplifier 12 and output from the speaker 13. .

  Thus, the broken curve Ce in FIG. 12 is the same as the broken curve Cb in FIG. 4 in that the resonance characteristic of the loud space 40 is greatly emphasized and the characteristic by feedback is also expressed. However, since the systems Se1 and Se2 of FIG. 11 have the phase inverting device 19, the configuration of the feedback loop of the systems Se1 and Se2 of FIG. 11 is not the same as the configuration of the feedback loop of the system Sb of FIG. Therefore, the characteristic due to feedback appearing on the broken line Ce in FIG. 12 is different from the characteristic due to feedback appearing on the broken line Cb in FIG.

  The frequency characteristic shown in FIG. 13 is a characteristic obtained by subtracting the characteristic of the actual curve Ca from the characteristic of the broken curve Ce of FIG. In FIG. 13, the frequencies having peaks in the positive direction are the frequency f1, the frequency f23, and the frequency f3. There is a high possibility that the frequency having a peak in the positive direction is a resonance frequency or a feedback frequency.

  Here, the characteristic shown in FIG. 5 is compared with the characteristic shown in FIG. The frequency characteristic of FIG. 5 shows a peak in the positive direction at frequency f1, frequency f21 and frequency f3, and the frequency characteristic of FIG. 13 shows a peak in the positive direction at frequency f1, frequency f23 and frequency f3. The frequency f1 and the frequency f3 are frequencies having a peak in the positive direction in common in the frequency characteristics of both drawings. The frequency f21 is a frequency that shows a peak in the positive direction only in the frequency characteristics of FIG. The frequency f23 is a frequency that shows a peak in the positive direction only in the frequency characteristics of FIG.

  The configuration of the feedback loop of the systems Se1 and Se2 in FIG. 11 is different from the configuration of the feedback loop of the system Sb in FIG. Therefore, the characteristic due to feedback appearing on the broken line Ce in FIG. 12 is different from the characteristic due to feedback appearing on the broken line Cb in FIG. Therefore, it can be considered that the frequency having a peak in the positive direction due to feedback in the frequency characteristic of FIG. 5 is different from the frequency having a peak in the positive direction due to feedback in the frequency characteristic of FIG. .

  On the other hand, the frequency having a peak in the positive direction due to the resonance of the loud space 40 can be considered to appear in both the frequency characteristics of FIG. 5 and the frequency characteristics of FIG.

  From the above, the frequency f1 and the frequency f3 are the resonance frequencies of the sound space 40, the frequency f21 is a feedback frequency based on the feedback loop of the system Sb in FIG. 3, and the frequency f23 is the feedback of the systems Se1 and Se2 in FIG. It can be thought of as a feedback frequency based on the loop.

  Therefore, for example, in the acoustic system of FIG. 1, the frequency f1 and the frequency f3 may be set as the center frequency of the dip for the dip filter 4.

  FIG. 14 is a schematic block diagram of the systems Sf1 and Sf2 including the detection devices 301 and 302 as an embodiment of the resonance frequency detection device according to the present invention. FIG. 14 (a) shows the detection device 301 and the system Sf1. FIG. 14B shows the detection device 302 and the system Sf2.

  The systems Sf1 and Sf2 include detection devices 301 and 302, an amplifier 12 that receives signals from the detection devices 301 and 302 and amplifies the power, a speaker 13 that receives an output signal from the amplifier 12 and amplifies the sound, and the speaker 13 radiates. And a microphone 14 for receiving a loud sound. The detection devices 301 and 302 receive the output signal of the microphone 14. The speaker 13 and the microphone 14 are arranged in a loudspeaker space (for example, a concert hall or a gymnasium) 40. The microphone 14 is disposed at a position where it can receive the reflected sound in the loudspeaker space 40 at a sufficiently large level with respect to the direct sound from the speaker 13.

  The detection devices 301 and 302 include a transmission unit 21, a measurement / control unit 25, a mixing unit 26, an opening / closing unit 27, a changeover switch 31, and a phase inverting device 32. The transmitting unit 21 functions as a sound source unit that generates a measurement signal. The measurement / control unit 25 functions as a control unit that controls each unit in the detection devices 301 and 302, and also functions as a measurement unit that measures frequency characteristics. Further, the phase inverting device 32 functions as a phase inverting means. The mixing unit 26, the opening / closing unit 27, the changeover switch 31, and the phase inverting device 32 constitute a signal switching means.

  In the systems Sf1 and Sf2, in the detection devices 301 and 302, the measurement / control unit 25 controls the transmission unit 21 to cause the transmission unit 21 to output a measurement signal. This measurement signal is a sine wave signal whose frequency changes with time, that is, a sine wave sweep signal. In the sine wave sweep signal, the level of the sine wave is constant at each time point during the frequency sweep.

  The mixing unit 26 synthesizes (mixes) the signal from the transmission unit 21 and the signal from the opening / closing unit 27 and outputs the combined signal (mixing signal). The signal input to the amplifier 12 is amplified in power and input to the speaker 13, and is emitted from the speaker 13 as a loud sound to the loudspeaker space 40. The sound in the loudspeaker space 40 is received by the microphone 14, and the output signal of the microphone 14 is input to the detection devices 301 and 302.

  In the detection apparatus 301 of FIG. 14A, the output signal of the microphone 14 is branched and sent to the measurement / control unit 25 and the switch 27. Further, the output signal of the mixing unit 26 is branched and sent to the phase inverter 32 and the changeover switch 31. The output signal of the phase inverting device 32 is also sent to the changeover switch 31. A signal from the changeover switch 31 is input to the amplifier 12.

  In the detection device 302 of FIG. 14B, the output signal of the microphone 14 is branched and sent to the measurement / control unit 25, the phase inverting device 32, and the changeover switch 31. The output signal of the phase inverting device 32 is sent to the changeover switch 31. The changeover switch 31 is connected to the opening / closing part 27. Then, the output signal of the mixing unit 26 is input to the amplifier 12.

  The measurement / control unit 25 of the detection devices 301 and 302 has a band-pass filter whose center frequency changes with time. This band pass filter temporally changes the center frequency in response to a temporal change in the frequency of the sine wave sweep signal transmitted by the transmission unit 21. Therefore, the measurement / control unit 25 can measure the amplitude characteristic of the frequency at that time point by detecting the level of the output signal of the microphone 14 through this bandpass filter.

  The measurement / control unit 25 can control the opening / closing of the opening / closing unit 27. Therefore, the open / close unit 27 can be set to the “open” state, and only the measurement signal from the transmitting unit 21 can be amplified from the speaker 13, or the open / close unit 27 can be set to the “closed” state and the measurement from the transmitting unit 21 can be performed. The loudspeaker 13 and the output signal of the microphone can be amplified from the speaker 13.

  Further, the measurement / control unit 25 can control the state of the changeover switch 31. Therefore, whether the output signal of the microphone 14 is amplified from the speaker 13 without inverting the phase, or whether the output signal of the microphone 14 is inverted by passing the phase inverting device 32 and then output from the speaker 13. You can choose.

  When the opening / closing part 27 is set to the “open” state, the same amplitude frequency characteristic as that measured by the system Sa of FIG. 2 can be measured.

  When the state of the changeover switch 31 is set so that the opening / closing section 27 is in the “closed” state and the output signal of the microphone 14 is amplified from the speaker 13 without phase inversion, the same as the measurement by the system Sb of FIG. Amplitude frequency characteristics can be measured.

  When the state of the changeover switch 31 is set so that the opening / closing unit 27 is in the “closed” state and the output signal of the microphone 14 is phase-inverted and then the loudspeaker 13 is turned on, the system Se1 and Se2 in FIG. Similar amplitude frequency characteristics can be measured.

  As described above, the resonance frequency of the sound space 40 can be detected from the amplitude frequency characteristic measured in this manner, separately from the feedback frequency. All the operations for detecting the resonance frequency from the measured amplitude frequency characteristic are performed by the measurement / control unit 25.

  The apparatus and method for detecting the resonance frequency separately from the feedback frequency by inverting the phase of the output signal from the microphone 14 disposed in the loudspeaker space 40 has been described above.

  In the apparatus and method described above (the apparatus and method described with reference to FIGS. 1 to 14), the transmitter or the transmitter transmits a sine wave sweep signal as a measurement signal. However, the measurement signal is not limited to the sine wave sweep signal, and various signals can be used. For example, it is possible to use a noise signal having a component within a predetermined frequency width and whose center frequency sweeps. In this case, the frequency width is preferably set to 1/3 octave or less. Moreover, it is more preferable to set it as 1/6 octave or less. Further, for example, pink noise can be used as the measurement signal. In this case, of course, the measuring instrument (measuring means) does not need to have a bandpass filter whose center frequency changes with time.

  Next, an apparatus and method for detecting a resonance frequency by outputting a reference frequency signal from a speaker arranged in a loudspeaker space will be described.

  FIG. 15 is a schematic block diagram of a system and a detection device (resonance frequency detection device) for detecting a resonance frequency in a loudspeaker space (for example, a concert hall or a gymnasium) 40.

  The system Sg shown in FIG. 15 has a transmitter 111 as a sound source means for generating a measurement signal, an amplifier 12 for inputting a signal generated by the transmitter 111 and amplifying the power, and an output signal of the amplifier 12 for input. A speaker 13, a microphone 14 that receives a loud sound emitted from the speaker 13, and a measurement / control unit 115 that inputs an output signal of the microphone 14 are provided. The microphone 14 may be a sound level meter. The measurement / control unit 115 controls the transmitter 111. That is, the frequency of the measurement signal output from the transmitter 111 and the time interval of the measurement signal can be controlled. The measurement / control unit 115 also functions as a measurement unit that measures the attenuation characteristics of the output signal of the microphone 14. The transmitter 111 and the measurement / control unit 115 constitute a detection device 400.

  The speaker 13 and the microphone 14 are disposed in the loudspeaker space 40. The microphone 14 is disposed at a position where it can receive the reflected sound in the loudspeaker space 40 at a sufficiently large level with respect to the direct sound from the speaker 13.

  The measurement signal output from the transmitter 111 of the system Sg is a signal in which the reference frequency signal is intermittently repeated a plurality of times. The reference frequency signal here is a sine wave signal having a specific frequency or a signal having a component within a predetermined frequency width centered on the specific frequency. The signal having a component within a predetermined frequency width centered on a specific frequency is, for example, a noise signal having a frequency component of 1/3 octave width centered on 200 Hz. If such a reference frequency signal is used, it becomes difficult to be affected by noise such as background noise, and measurement with high reliability becomes possible.

  FIG. 16 is a diagram showing the signal level of the measurement signal described above on the time axis. For example, a 200 Hz sine wave having a specific frequency is output for a duration of 0.1 seconds, and then output again for a duration of 0.1 seconds at a time interval of 0.9 seconds. Output is continued again for 0.1 seconds at intervals. In other words, a 200 Hz sine wave lasting 0.1 seconds intermittently at 1 second intervals is output.

  As shown in FIG. 16, in this embodiment, a 200 Hz sine wave lasting 0.1 seconds is output a plurality of times at equal time intervals. However, it is not always necessary to output the sine wave at equal time intervals. Absent. For example, a sine wave having a specific frequency that lasts for a predetermined time may be output a plurality of times at random time intervals.

  FIG. 17 is a diagram showing the sound pressure level measured by the microphone 14 on the time axis. Three peak points are generated at intervals of one second so as to be synchronized with the measurement signal shown in FIG. However, the sound pressure level decays quickly. Thus, when the sound pressure level decays quickly in the loud space, the specific frequency (200 Hz) of the measurement signal is considered not to be a resonance frequency.

  FIG. 18 is a diagram showing, on the time axis, the sound pressure level measured by the microphone 14 when a measurement signal having a specific frequency of 250 Hz is output from the speaker 13 of the system Sg of FIG. A reference frequency signal having a specific frequency of 250 Hz is output from the transmitter 111 for 0.1 seconds, and then output again for 0.1 seconds at a time interval of 0.9 seconds. The output is continued for 0.1 second again at a time interval of 9 seconds. That is, a 250 Hz sine wave is output intermittently 3 times at intervals of 1 second and lasting 0.1 seconds.

  As understood from FIG. 18, in the sound pressure level measured in the loud sound space 40, three peak points are generated at intervals of one second so as to be synchronized with the measurement signal. The sound pressure level is moderately attenuated. Thus, when the sound pressure level is moderately attenuated in the sound space 40, it is considered that the specific frequency (250 Hz) of the measurement signal may be the resonance frequency of the sound space 40.

  In this way, if the resonance frequency is determined from the sound pressure level attenuation characteristics in the sound expansion space 40, the reference frequency signal does not necessarily have to be radiated from the speaker 13 a plurality of times. For example, a reference frequency signal lasting several seconds can be emitted from the speaker 13 only once, and the resonance frequency can be determined from the sound pressure level attenuation characteristics in the loudspeaker space 40. For example, it can also be determined by whether or not it decays more slowly than a predetermined speed.

  In addition, in order to determine whether the sound pressure level decays slowly or rapidly in the sound space 40, for example, on the diagram showing the sound pressure level on the time axis as shown in FIG. The determination may be made by calculating the area of the area surrounded by the level curve. That is, if the area is small, it is judged that the sound pressure level is rapidly attenuated, and if the area is large, it is judged that the sound pressure level is moderately attenuated.

  FIG. 19 is a diagram showing on the time axis the sound pressure level measured by the microphone 14 when a measurement signal having a specific frequency of 300 Hz is output from the speaker 13 of the system Sg of FIG. A reference frequency signal having a specific frequency of 300 Hz is output from the transmitter 111 for 0.1 seconds, and then output again for 0.1 seconds at a time interval of 0.9 seconds. The output is continued for 0.1 second again at a time interval of 9 seconds. That is, a 300 Hz sine wave lasting 0.1 seconds intermittently at 1 second intervals is output.

  As can be understood from FIG. 19, in the sound pressure level measured in the loud sound space 40, three peak points are generated at intervals of one second so as to be synchronized with the measurement signal. The sound pressure level is moderately attenuated. Moreover, the attenuation from the second peak is more gradual than the attenuation from the first peak, and the attenuation from the third peak is more gradual than the attenuation from the second peak. The reason why the attenuation gradually decreases in this way is considered to be because the energy of the loud sound output last time remains sufficiently in the loud sound space 40 until the next loud sound is output. In such a case, it is considered that there is a high possibility that the specific frequency (300 Hz) of the measurement signal is the resonance frequency of the sound space 40.

  The resonance frequency of the sound space 40 can be detected by determining the state of the sound pressure level attenuation process of the sound space 40 while gradually changing the specific frequency of the measurement signal by the measurement / control unit 115. . As one of the forms in which the specific frequency of the measurement signal is gradually changed, for example, a form in which the specific frequency is raised step by step by 1/4 octave can be employed.

  FIG. 20 is a schematic block diagram of a system and a detection device (resonance frequency detection device) for detecting a resonance frequency in a loudspeaker space (for example, a concert hall or a gymnasium) 40.

  Similarly to the system Sg in FIG. 15, the system Sh in FIG. 20 also includes a transmitter 111 serving as a sound source unit that emits a measurement signal, an amplifier 12, a speaker 13 that receives an output signal from the amplifier 12, and a speaker 13. The microphone 14 which receives the loud sound emitted by 13 and the measurement / control unit 115 which inputs the output signal of the microphone 14 are provided. The measurement / control unit 115 can control the frequency of the measurement signal output from the transmitter 111 and the time interval of the measurement signal. The measurement / control unit 115 also functions as a measurement unit that measures the attenuation characteristics of the output signal of the microphone 14.

  The detection device 500 includes a transmitter 111, a measurement / control unit 115, and a mixing device 116.

  The system Sh of FIG. 20 is different from the system Sg of FIG. 15 in that the measurement signal from the transmitter 111 and the output signal of the microphone 14 are mixed (synthesized) by the mixing device 116 in the system Sh of FIG. The synthesized signal is sent to the amplifier 12. The mixing device 116 functions as signal output means. As described above, when such a feedback loop is provided, the resonance of the loud space 40 is measured with more emphasis.

  The system Sh in FIG. 20 can also detect the resonance frequency of the loud space 40 as in the system Sg in FIG. Moreover, the resonance frequency can be detected more clearly than when the system Sg of FIG. 15 is used.

  FIG. 21 is a schematic block diagram of a system and a detection device (resonance frequency detection device) for detecting a resonance frequency in a loudspeaker space (for example, a concert hall or a gymnasium) 40, and FIG. FIG. 21B shows the system 601 and the detection device 602.

  Similarly to the system Sg in FIG. 15, the systems Si1 and Si2 in FIG. 21 also have a transmitter 111 as a sound source means for generating a measurement signal, an amplifier 12, and a speaker 13 that receives an output signal from the amplifier 12 and amplifies the sound. The microphone 14 that receives the loud sound emitted from the speaker 13 and the measurement / control unit 115 that receives the output signal of the microphone 14 are provided. The measurement / control unit 115 can control the frequency of the measurement signal output from the transmitter 111 and the time interval of the measurement signal. The measurement / control unit 115 also functions as a measurement unit that measures the attenuation characteristics of the output signal of the microphone 14.

  In the system Si1 in FIG. 21A, the detection device 601 includes a transmitter 111, a measurement / control unit 115, a mixing unit 116, and a delay device 128. The measurement signal from the transmitter 111 and the output signal of the microphone 14 input by the detection device 601 are combined by the mixing unit 116, and the combined signal is output from the detection device 601 via the delay device 128. The output signal of the detection device 601 is sent to the amplifier 12. Further, the output signal of the microphone 14 input by the detection device 601 is branched and sent to the measurement / control unit 115 and the mixing unit 116.

  In the system Si2 of FIG. 21B, the detection device 602 includes a transmitter 111, a measurement / control unit 115, a mixing unit 116, and a delay device 128. The measurement signal from the transmitter 111 and the output signal of the delay device 128 are combined by the mixing unit 116, and the combined signal is output from the detection device 601. The output signal of the microphone 14 input by the detection device 601 is branched and sent to the delay device 128 and the measurement / control unit 115.

  The system Si1 and Si2 in FIG. 21 are different from the system Sg in FIG. 15 in that the measurement signal from the transmitter 111 is amplified from the speaker 13 and the delay device 128 is used in the system Si1 and Si2 in FIG. The output signal of the microphone 14 that has passed through is amplified. As described above, when such a feedback loop is provided, the resonance of the loud space 40 is measured with more emphasis. In the detection devices 601 and 602 for the systems Si1 and Si2, the mixing unit 116 and the delay device 128 constitute a signal output unit.

  The delay device 128 is controlled by the measurement / control unit 115. That is, the measurement / control unit 115 can arbitrarily set the delay time of the delay device 128 within a predetermined time range. For example, the delay device 128 can set the delay time of the delay device 128 to 0 msec, can be set to 1 msec, or can be set to 2 msec.

  Also in the measurement using the systems Si1 and Si2, for example, a sine wave having a specific frequency of 250 Hz is output from the oscillator 111 continuously for 0.1 second, and then again at a time interval of 0.9 second. It is possible to output continuously for a second, and then output again continuously for 0.1 seconds with a time interval of 0.9 seconds. In other words, a 250 Hz sine wave lasting 0.1 seconds is output intermittently at intervals of 1 second.

  FIG. 22 is a diagram showing, on the time axis, the sound pressure level measured by the microphone 14 when the measurement signal as described above is output from the oscillator 111 of the detection devices 601 and 602. FIG. However, at this time, the delay time of the delay device 128 is set to 0 ms.

  As understood from FIG. 22, the sound pressure level curve has three peak points at intervals of one second so as to synchronize with the measurement signal. The sound pressure level is moderately attenuated. Thus, when the sound pressure level is gradually attenuated in the loud space, it is considered that the specific frequency (250 Hz) of the measurement signal may be the resonance frequency of the loud space 40. However, there is a possibility that this specific frequency (250 Hz) is not a resonance frequency but a feedback frequency. Even if the specific frequency (250 Hz) is the feedback frequency, the sound pressure level is gradually attenuated.

  Therefore, in order to determine whether the specific frequency (250 Hz) is the resonance frequency or the feedback frequency, the same measurement is performed while changing the delay time of the delay device 128. The oscillator 111 intermittently outputs a 250 Hz sine wave lasting 0.1 seconds three times. When the sound pressure level of the loudspeaker space 40 is measured in synchronization with the first output, the delay of the delay device 128 is performed. For example, when the time is set to 0 ms and the sound pressure level of the loudspeaker space 40 is measured in synchronization with the second output, the delay time of the delay device 128 is set to 1 ms, for example, and is synchronized with the third output. When measuring the sound pressure level of the loud space 40, the delay time of the delay device 128 is set to 2 milliseconds, for example.

  Since the resonance frequency is determined only by the characteristics of the sound space 40, it does not change even if the configuration of the feedback loop changes. If the specific frequency (250 Hz) is the resonance frequency, even if the delay time of the delay device 128 is changed, the rate of attenuation of the sound pressure level measured in the loudspeaker space 40 does not change.

  However, the feedback frequency changes as the configuration of the feedback loop changes. When the delay time of the delay device 128 is changed, the configuration of the feedback loop is changed. Therefore, if the specific frequency (250 Hz) is the feedback frequency when the delay time of the delay device 128 is set to 0 ms, the sound pressure measured in the loudspeaker space 40 when the delay time of the delay device 128 is changed. The rate of level decay also changes.

  FIG. 23 shows the sound pressure level measured by the microphone 14 on the time axis when the measurement signal as described above is output from the oscillator 111 while changing the delay time of the delay device 128 as described above. FIG. Strictly speaking, the sound pressure level curve measured by the system Si1 in FIG. 21 (a) and the sound pressure level curve measured by the system Si2 in FIG. 21 (b) are not the same. Explain without.

  As understood from FIG. 23, the sound pressure level curve has three peak points at intervals of one second so as to be synchronized with the measurement signal. The sound pressure level in the loudspeaker space 40 corresponding to the first output from the oscillator 111 is gradually attenuated. The sound pressure level in the loudspeaker space 40 corresponding to the second output attenuates relatively quickly. The sound pressure level of the loudspeaker space 40 corresponding to the third output is slightly attenuated.

  As described above, since the speed of attenuation of the sound pressure level in the sound space 40 is changed by changing the delay time of the delay device 128, the specific frequency (250 Hz) of the measurement signal is not the resonance frequency. Judgment can be made.

  The measurement / control unit 115 feedbacks the resonance frequency of the sound space 40 by determining the state of the sound pressure level attenuation process of the sound space 40 as described above while gradually changing the specific frequency of the measurement signal. It can be detected separately from the frequency.

  FIG. 24 is a schematic block diagram of a system and a detection device (resonance frequency detection device) for detecting a resonance frequency in a loudspeaker space (for example, a concert hall or a gymnasium) 40. FIG. 24 (a) shows a system Sj1, A detection device 701 is shown, and FIG. 24B shows a system Sj2 and a detection device 702.

  Similarly to the system Sg in FIG. 15, the systems Sj1 and Sj2 in FIG. 24 also have a transmitter 111 that is a sound source means for generating a measurement signal, an amplifier 12, and a speaker 13 that receives the output signal of the amplifier 12 and amplifies it. The microphone 14 that receives the loud sound emitted from the speaker 13 and the measurement / control unit 115 that receives the output signal of the microphone 14 are provided. The measurement / control unit 115 can control the frequency of the measurement signal output from the transmitter 111 and the time interval of the measurement signal. The measurement / control unit 115 also functions as a measurement unit that measures the attenuation characteristics of the output signal of the microphone 14.

  24A includes a transmitter 111 serving as a sound source unit, a measurement / control unit 115, a mixing unit 116, a changeover switch 131, and a phase inverting device 132. In the detection device 701, the output signal of the microphone 14 is branched and sent to the measurement / control unit 115 and the mixing unit 116. The measurement signal from the transmitter 111 is also input to the mixing unit 116. The mixing unit 116 combines the output signal of the microphone 14 and the measurement signal from the transmitter 111, and the combined signal is branched and sent to the phase inverter 132 and the changeover switch 131. The output signal of the phase inverter 132 is also sent to the changeover switch 131. Then, a signal from the changeover switch 131 is sent to the amplifier 12.

  24B includes a transmitter 111 serving as a sound source unit, a measurement / control unit 115, a mixing unit 116, a changeover switch 131, and a phase inverting device 132. In the detection device 702, the output signal of the microphone 14 is branched and sent to the measurement / control unit 115, the phase inverting device 132, and the changeover switch 131. The output signal of the phase inverter 132 is sent to the changeover switch 131. The output signal of the changeover switch 31 is sent to the mixing unit 116. The measurement signal from the transmitter 111 is also input to the mixing unit 116. The mixing unit 116 combines the measurement signal from the transmitter 111 and the signal from the changeover switch 131, and sends this combined signal to the amplifier 12.

  In the systems Sj1 and Sj2, the measurement signal is amplified from the speaker 13. In addition, the output signal of the microphone 14 or a phase inversion signal obtained by inverting the phase of the output signal of the microphone 14 is amplified from the speaker 13. In the detection devices 701 and 702 of the systems Sj1 and Sj2, the mixing unit 116, the changeover switch 131, and the phase inverting device 132 constitute a signal output unit.

  By switching the selector switch 131, the speaker 13 can select whether the output signal of the microphone 14 is to be loudened without being phase-inverted or to be loudened after being phase-inverted. The changeover switch 131 is controlled by the measurement / control unit 115. Therefore, the measurement / control unit 115 can select from the speaker 13 whether the output signal of the microphone 14 is to be loudened without phase inversion, or to be loudened after the phase is inverted.

  The systems Sj1 and Sj2 also include feedback loops. However, as described above, the resonance of the sound space 40 is more emphasized and measured when such feedback loops are provided.

  When the selector switch 131 is set so that the output signal of the microphone 14 is amplified from the speaker 13 without phase inversion, and the selector switch 131 is set so that the output signal of the microphone 14 is inverted from the phase and then output from the speaker 13 The configuration of the feedback loop is different from that when it is done.

  Also in the measurement by the systems Sj1 and Sj2, for example, a sine wave having a specific frequency of 250 Hz is output from the oscillator 111 continuously for 0.1 second, and then again at a time interval of 0.9 second. It is possible to output continuously for a second, and then output again continuously for 0.1 seconds with a time interval of 0.9 seconds. In other words, a 250 Hz sine wave lasting 0.1 seconds is output intermittently at intervals of 1 second.

  FIG. 25 is a diagram showing, on the time axis, the sound pressure level measured by the microphone 14 when the measurement signal as described above is output from the oscillator 111 in the systems Sj1 and Sj2. However, at this time, the state of the selector switch 131 is set so that the output signal of the microphone 14 can be amplified from the speaker 13 without inverting the phase.

  As understood from FIG. 25, the sound pressure level curve has three peak points at intervals of one second so as to be synchronized with the measurement signal. The sound pressure level is moderately attenuated.

  As described above, when the sound pressure level is moderately attenuated in the loud space, it is considered that the specific frequency (250 Hz) of the measurement signal may be the resonance frequency of the loud space 40. There is also a possibility that (250 Hz) is not a resonance frequency but a feedback frequency. Even if the specific frequency (250 Hz) is the feedback frequency, the sound pressure level is gradually attenuated.

  Therefore, in order to determine whether the specific frequency (250 Hz) is the resonance frequency or the feedback frequency, the same measurement is performed while the changeover switch 131 is switched. The oscillator 111 intermittently outputs a 250 Hz sine wave lasting 0.1 seconds three times. For example, when measuring the sound pressure level of the loudspeaker space 40 in synchronization with the first output, the microphone 14 is used. When the change-over switch 131 is set so that the output signal of the sound can be amplified by the speaker 13 without inverting the phase, and the sound pressure level of the sound expansion space 40 is measured in synchronization with the second output, the microphone 14 When the changeover switch 131 is set to a state where the output signal is phase-inverted by the phase inverter 132 and can be amplified by the speaker 13, and the sound pressure level of the loudspeaker space 40 is measured in synchronization with the third output, The changeover switch 131 is set so that the output signal of the microphone 14 can be amplified by the speaker 13 without inverting the phase.

  As described above, the resonance frequency is determined only by the characteristics of the sound space 40, and does not change even if the configuration of the feedback loop changes. If the specific frequency (250 Hz) is the resonance frequency, the speed of attenuation of the sound pressure level in the sound space 40 does not change even if the configuration of the feedback loop changes.

  However, as described above, the feedback frequency changes due to a change in the configuration of the feedback loop. The configuration of the feedback loop that does not invert the phase of the output signal of the microphone 14 and the feedback loop that inverts the phase of the output signal of the microphone 14 are different. Therefore, if the specific frequency (250 Hz) is a feedback frequency resulting from a feedback loop that does not invert the phase of the output signal of the microphone 14, the configuration of the feedback loop is set to invert the phase of the output signal of the microphone 14. When changed, the speed of attenuation of the sound pressure level in the loud space 40 also changes.

  FIG. 26 shows on the time axis the sound pressure level measured by the microphone 14 when the measurement signal as described above is output from the oscillator 111 while switching the changeover switch 131 in the systems Sj1 and Sj2. FIG. Strictly speaking, the sound pressure level curve measured by the system Sj1 in FIG. 24 (a) and the sound pressure level curve measured by the system Sj2 in FIG. 24 (b) are not the same. Explain without.

  As understood from FIG. 26, the sound pressure level curve has three peak points at intervals of one second so as to be synchronized with the measurement signal. When the sound pressure level in the loudspeaker space 40 is measured in synchronization with the first output from the oscillator 111, the sound pressure level is gradually attenuated. When the sound pressure level of the loudspeaker space 40 is measured in synchronization with the second output, the sound pressure level is rapidly attenuated. When the sound pressure level of the loudspeaker space 40 is measured in synchronization with the third output, the sound pressure level is gradually attenuated.

  In this way, the speed of attenuation of the sound pressure level in the loudspeaker space 40 changes depending on whether the output signal of the microphone 14 is phase-inverted and loudspeaked by the speaker 13 or by the speaker 13 without being phase-inverted. Therefore, it can be determined that the specific frequency (250 Hz) of the measurement signal is not a resonance frequency.

  The measurement / control unit 115 feedbacks the resonance frequency of the sound space 40 by determining the state of the sound pressure level attenuation process of the sound space 40 as described above while gradually changing the specific frequency of the measurement signal. It can be detected separately from the frequency.

  The various apparatuses and methods for detecting the resonance frequency in the sound space 40 have been described above with reference to FIGS.

  Next, a method for selecting a frequency to be set as the center frequency of the dip in the dip filter 4 (see FIG. 1) from the resonance frequencies thus detected will be described.

  First, it has been described that the frequency characteristics as shown in FIG. 4 and the frequency characteristics as shown in FIG. 5 can be obtained by the measurement using the system Sa in FIG. 2 and the system Sb in FIG. Furthermore, it has been explained that the frequency f1, the frequency f21, and the frequency f3, which are frequencies that show peaks in the positive direction in the characteristic curve Db of FIG. 5, are likely to be resonance frequencies or feedback frequencies.

  Hereinafter, in order to simplify the explanation, the dip filter 4 (see FIG. 1) is set as the center frequency of the dip on the assumption that all of these frequencies (frequency f1, frequency f21 and frequency f3) are resonance frequencies. How to select the frequency to be described will be described.

First, a predetermined number of frequencies out of the frequency f1, the frequency f21, and the frequency f3 are selected as candidates for the center frequency of the dip to be set as the removal frequency in the dip filter 4.
Specifically, candidate frequencies are selected from these frequencies in descending order of the amplitude level of the curve Cb in FIG.

  FIG. 27 is a characteristic diagram in which only the curve Cb is extracted from FIG. In FIG. 27, the vertical axis and the horizontal axis are logarithmic axes, the vertical axis indicates the amplitude level, and the horizontal axis indicates the frequency. In the curve Cb of FIG. 27, the amplitude level at the frequency f21 is the largest, the amplitude level at f3 is the next largest, and the amplitude level at the f1 is the next largest. Here, if the number of frequencies to be selected as candidates is “3”, all of the frequency f1, the frequency f21, and the frequency f3 are candidate frequencies. If the number of frequencies selected as candidates is “2”, the frequencies f21 and f3 are the candidate frequencies.

  Then, the center frequency of the dip to be set in the dip filter 4 may be determined according to the priority order based on the magnitude of the amplitude level of the curve Cb in FIG. Therefore, if the number of dip to be set in the dip filter 4 of FIG. 1 is “2”, for example, the frequency f21 and the frequency f3 are set as the center frequency of the dip of the dip filter 4. For example, if the number of dip to be set in the dip filter 4 of FIG. 1 is “1”, only the frequency f 21 is set as the center frequency of the dip of the dip filter 4.

  In this way, the center frequency of the dip to be set in the dip filter 4 may be finally determined by the priority order based on the magnitude of the amplitude level of the curve Cb in FIG. 27, but the amplitude of the curve Cb in FIG. After selecting a plurality of dip center frequency candidates to be set in the dip filter 4 according to the priority order based on the level magnitude, the candidate (dip filter) is further selected based on the magnitude of the amplitude level in the curve Db of FIG. The order of the dip center frequency candidates) to be set may be changed.

  Now, it is assumed that the frequency f1, the frequency f21, and the frequency f3 are all candidate frequencies by selection based on the magnitude of the amplitude level of the curve Cb in FIG. Next, the candidate rank is changed to these candidate frequencies (frequency f1, f21, f3). The ranking is set higher from the highest amplitude level in the amplitude frequency characteristic curve Db of FIG. Among the frequencies f1, f21, and f3, the frequency f3 has the largest amplitude level in the curve Db of FIG. 5, the frequency level having the next largest amplitude level is the frequency f21, and the next largest amplitude level is the frequency f21. The frequency is f1. Therefore, the frequency f3 is the frequency of the first candidate, the frequency f21 is the frequency of the second candidate, and the frequency f1 is the frequency of the third candidate.

  If the number of dip to be set in the dip filter 4 of FIG. 1 is “2”, for example, the frequency f3 and the frequency f21 are set as the center frequency of the dip of the dip filter 4. For example, if the number of dip to be set in the dip filter 4 of FIG. 1 is “1”, only the frequency f3 is set as the center frequency of the dip of the dip filter 4.

  In this way, the center frequency of the dip to be set in the dip filter 4 can be objectively selected without requiring experience or skill. By doing so, resonance in the loudspeaker space 40 of FIG. 1 can be effectively prevented.

  In addition, after selecting candidates of center frequencies of a plurality of dips to be set in the dip filter 4 according to the priority order based on the magnitude of the amplitude level of the curve Cb in FIG. 27, the magnitude of the amplitude level in the curve Db in FIG. Based on this, the order of candidates (candidates for the center frequency of the dip to be set in the dip filter) has been changed for the following reason. That is, the curve Cb in FIG. 27 includes not only the characteristics due to the resonance of the sound space 40 but also the amplitude frequency characteristics of the electroacoustic system (system consisting of the amplifier 12, the speaker 13, the microphone 14, etc.). This characteristic greatly depends not only on the resonance characteristics but also on the amplitude frequency characteristics of the electroacoustic system. On the other hand, the curve Db in FIG. 5 shows the characteristic due to the resonance of the sound space 40, and the influence of the amplitude frequency characteristic of the electroacoustic system is small. Therefore, it is more effective to prevent the resonance of the sound space 40 by finally determining the center frequency of the dip to be set in the dip filter 4 based on the magnitude of the amplitude level in the curve Db of FIG. is there.

  The above resonance frequency selection method is also effective when the number of dips to be set in the dip filter and the number of detected resonance frequencies are larger. For example, when there are 200 or more detected resonance frequencies, 120 frequencies having a large amplitude level in curve Cb in FIG. 27 may be left as candidates, and the remaining frequencies may be excluded from candidates. Further, the ranks of candidates are reassigned to the 120 frequencies based on the magnitude of the amplitude level in the curve Db in FIG. 5, and the frequencies up to the top 8 in the reassigned ranks are sent to the dip filter as the center frequency of the dip. You may make it set as.

  The embodiment of the present invention has been described above based on FIGS.

  In the above-described embodiment, the example of applying the resonance frequency detection method and the device thereof according to the present invention to the detection of the resonance frequency in the sound space where the acoustic equipment is arranged has been described. The present invention can be applied not only to such a loud space but also to any space (sound space) in which resonance frequency detection is required. For example, in order to know the liquid filling amount in the liquid tank, the present invention can be applied to a technique for measuring the volume of a space not filled with liquid in the tank by detecting the resonance frequency.

  According to the present invention, it is possible to accurately detect the resonance frequency without requiring experience or skill, and it is possible to appropriately select the frequency to be set as the center frequency of the dip in the dip filter. Therefore, it is useful in the technical field of electroacoustics, for example.

It is a schematic block diagram of the acoustic system installed in the loudspeaker space (for example, a concert hall or a gymnasium). It is a schematic block diagram of a system for measuring amplitude frequency characteristics in a loudspeaker space (for example, a concert hall or a gymnasium). 1 is a schematic block diagram of a system for measuring amplitude frequency characteristics in a loudspeaker space. FIG. FIG. 4 is a characteristic diagram schematically showing the amplitude frequency characteristic of the loud space measured by the system of FIG. 2 and the amplitude frequency characteristic of the loud space measured by the system of FIG. 3. FIG. 5 is a frequency characteristic diagram obtained by subtracting the characteristic of the actual curve Ca from the characteristic of the broken curve Cb of FIG. 4. 1 is a schematic block diagram of a system for measuring amplitude frequency characteristics in a loudspeaker space. FIG. FIG. 7 is a characteristic diagram schematically showing the amplitude frequency characteristic of the loud space measured by the system of FIG. 2 and the amplitude frequency characteristic of the loud space measured by the system of FIG. 6. FIG. 8 is a frequency characteristic diagram obtained by subtracting the characteristic of the actual curve Ca from the characteristic of the broken curve Cc of FIG. 7. 1 is a schematic block diagram of a system including a detection device as one embodiment of a resonance frequency detection device according to the present invention. It is a figure which shows the example of a structure which can be employ | adopted as a delay apparatus in the detection apparatus of FIG. 1 is a schematic block diagram of a system for measuring amplitude frequency characteristics in a loudspeaker space. FIG. FIG. 12 is a characteristic diagram schematically showing the amplitude frequency characteristic of the loud space measured by the system of FIG. 2 and the amplitude frequency characteristic of the loud space measured by the system of FIG. 11. FIG. 13 is a frequency characteristic diagram obtained by subtracting the characteristic of the actual curve Ca from the characteristic of the broken curve Ce in FIG. 12. 1 is a schematic block diagram of a system including a detection device as one embodiment of a resonance frequency detection device according to the present invention. It is a schematic block diagram of a system for detecting a resonance frequency in a loudspeaker space (for example, a concert hall or a gymnasium). It is the figure which represented the signal level of the signal for a measurement on the time axis. It is the figure which represented on the time axis the sound pressure level measured with the microphone. It is the figure which represented on the time axis the sound pressure level measured with a microphone. It is the figure which represented on the time axis the sound pressure level measured with a microphone. It is a schematic block diagram of a system for detecting a resonance frequency in a loudspeaker space (for example, a concert hall or a gymnasium). It is a schematic block diagram of a system for detecting a resonance frequency in a loudspeaker space (for example, a concert hall or a gymnasium). It is the figure which represented on the time axis the sound pressure level measured with a microphone. It is the figure which represented on the time axis the sound pressure level measured with a microphone. It is a schematic block diagram of a system for detecting a resonance frequency in a loudspeaker space (for example, a concert hall or a gymnasium). It is the figure which represented on the time axis the sound pressure level measured with a microphone. It is the figure which represented on the time axis the sound pressure level measured with the microphone. FIG. 5 is a characteristic diagram in which only the curve Cb is extracted from FIG. 4.

Explanation of symbols

11 Transmitter
12 amplifiers
13 Speaker
14 Microphone
15 Measuring instrument
16 Mixing equipment
17 Delay device
19 Phase reversal device
21 Transmitter
25 Measurement / control section
26 Mixing section
27 Opening and closing part
28 Delay device
31 selector switch
32 Phase reversal device
40 Amplification space
111 Transmitter
115 Measurement / control section
116 mixing equipment
128 delay device
131 selector switch
132 Phase reversal device
201,202,301,302,400,500,601,602,701,702 Detector

Claims (16)

Attenuation characteristic measurement step of loudening a reference frequency signal lasting for a predetermined time from a speaker arranged in the resonance space, receiving a sound by a microphone arranged in the resonance space, and measuring an attenuation characteristic of the output signal of the microphone Prepared,
A resonance frequency detection method for detecting a resonance frequency of the resonance space based on the attenuation characteristic,
The resonance frequency detection method, wherein the reference frequency signal is a sine wave signal having a specific frequency or a signal having a component within a predetermined frequency width centered on the specific frequency. Attenuation characteristics of the output signal of the microphone by receiving a sound from a speaker arranged in the resonance space and a reference frequency signal lasting for a predetermined time and an output signal of the microphone arranged in the resonance space. A damping characteristic measuring step for measuring
A resonance frequency detection method for detecting a resonance frequency of the resonance space based on the attenuation characteristic,
The resonance frequency detection method, wherein the reference frequency signal is a sine wave signal having a specific frequency or a signal having a component within a predetermined frequency width centered on the specific frequency.   3. The resonance frequency detection method according to claim 1, wherein when the attenuation rate obtained from the attenuation characteristic is slower than a predetermined attenuation rate, the specific frequency of the reference frequency signal is determined as the resonance frequency. From a speaker arranged in the resonance space, a reference frequency signal that is intermittently repeated a plurality of times and a delayed signal obtained by delaying the output signal of the microphone arranged in the resonance space by a delay time of 0 or more, Attenuating characteristic measurement step of receiving sound by the microphone and measuring the attenuation characteristic of the output signal of the microphone,
A resonance frequency detection method for detecting a resonance frequency of the resonance space based on the attenuation characteristic,
In synchronization with the intermittent repetition of the reference frequency signal, the delay time changes,
The resonance frequency detection method, wherein the reference frequency signal is a sine wave signal having a specific frequency or a signal having a component within a predetermined frequency width centered on the specific frequency.   It is determined whether or not the attenuation characteristic changes due to the change in the delay time, and when it is determined that the attenuation characteristic changes due to the change in the delay time, the specific frequency of the reference frequency signal is changed. The resonance frequency detection method according to claim 4, wherein the resonance frequency is not determined. A first loudspeaking state in which a reference frequency signal that is intermittently repeated a plurality of times and a microphone output signal that is disposed in the resonance space are loudspeaked from a speaker disposed in the resonant space, or the intermittently repeated multiple times. A second loudspeaking state for loudening a reference frequency signal to be produced and a phase inversion signal obtained by inverting the phase of the output signal of the microphone arranged in the resonance space, and receiving the sound by the microphone, and outputting the output signal of the microphone Attenuation characteristic measurement process for measuring the attenuation characteristic of
A resonance frequency detection method for detecting a resonance frequency of the resonance space based on the attenuation characteristic,
In synchronization with the intermittent repetition of the reference frequency signal, the loudness state is changed from the first loudness state to the second loudness state, or from the second loudspeaking state to the first loudness state,
The resonance frequency detection method, wherein the reference frequency signal is a sine wave signal having a specific frequency or a signal having a component within a predetermined frequency width centered on the specific frequency. Determining whether the attenuation characteristic changes due to the change of the loudness state,
The resonance frequency detection method according to claim 6, wherein when it is determined that the attenuation characteristic changes due to the change of the loudness state, the specific frequency of the reference frequency signal is not determined as the resonance frequency.   The resonance frequency detection method according to any one of claims 1 to 7, wherein the attenuation characteristic measurement step is repeated a plurality of times while changing a specific frequency of the reference frequency signal. A sound source means and a measuring means,
The sound source means can generate and output a measurement signal,
The measurement signal is a reference frequency signal lasting a predetermined time,
The reference frequency signal is a sine wave signal of a specific frequency or a signal having a component within a predetermined frequency width centered on the specific frequency,
The measurement means can input an output signal of a microphone,
The measurement means is a resonance frequency detection device that measures an attenuation characteristic of an output signal of the microphone and detects a resonance frequency based on the attenuation characteristic. A sound source means, a signal output means, and a measuring means;
The sound source means generates a measurement signal,
The measurement signal is a reference frequency signal lasting a predetermined time,
The reference frequency signal is a sine wave signal of a specific frequency or a signal having a component within a predetermined frequency width centered on the specific frequency,
The signal output means can input the measurement signal from the sound source means and the output signal of the microphone,
The signal output means is capable of outputting the measurement signal and the output signal of the microphone so that they can be amplified by a speaker.
The measurement means can input an output signal of the microphone,
The measurement means is a resonance frequency detection device that measures an attenuation characteristic of an output signal of the microphone and detects a resonance frequency based on the attenuation characteristic.   The measuring means determines whether or not the attenuation rate obtained from the attenuation characteristic is slower than a predetermined attenuation rate, and when determining that the attenuation rate obtained from the attenuation characteristic is slower than the predetermined attenuation rate, The resonance frequency detection apparatus according to claim 9 or 10, wherein a specific frequency of the reference frequency signal is determined as the resonance frequency. A sound source means, a signal output means, and a measuring means;
The sound source means generates a measurement signal,
The measurement signal is a reference frequency signal that is intermittently repeated a plurality of times,
The reference frequency signal is a sine wave signal of a specific frequency or a signal having a component within a predetermined frequency width centered on the specific frequency,
The signal output means can input the measurement signal from the sound source means and the output signal of the microphone,
The signal output means is capable of outputting the measurement signal and a delayed signal obtained by delaying the output signal of the microphone by a delay time of 0 or more by a speaker.
The signal output means changes the delay time in synchronization with intermittent repetition of the reference frequency signal,
The measurement means can input an output signal of the microphone,
The measurement means is a resonance frequency detection device that measures an attenuation characteristic of an output signal of the microphone and detects a resonance frequency based on the attenuation characteristic.   The measuring means determines whether or not the attenuation characteristic changes due to the change in the delay time, and determines that the attenuation characteristic changes due to the change in the delay time. The resonance frequency detection apparatus according to claim 12, wherein the specific frequency of the signal is not determined as the resonance frequency. A sound source means, a signal output means, and a measuring means;
The sound source means generates a measurement signal,
The measurement signal is a reference frequency signal that is intermittently repeated a plurality of times,
The reference frequency signal is a sine wave signal of a specific frequency or a signal having a component within a predetermined frequency width centered on the specific frequency,
The signal output means can input the measurement signal from the sound source means and the output signal of the microphone,
The signal output means outputs a state of the first output state for outputting the measurement signal and the output signal of the microphone through a speaker, or the phase of the measurement signal and the output signal of the microphone. Can be selectively set to a second output state in which a phase-inverted signal obtained by inverting the signal is output for the purpose of loudening the speaker.
The state of the signal output means is changed from the first output state to the second output state or from the second output state to the first output state in synchronization with intermittent repetition of the reference frequency signal. And
The measurement means can input an output signal of the microphone,
The measurement means is a resonance frequency detection device that measures an attenuation characteristic of an output signal of the microphone and detects a resonance frequency based on the attenuation characteristic.   The measuring means determines whether or not the attenuation characteristic changes due to a change in the state of the signal output means, and determines that the attenuation characteristic changes due to a change in the state of the signal output means The resonance frequency detection apparatus according to claim 14, wherein the specific frequency of the reference frequency signal is not determined as a resonance frequency. The sound source means generates a measurement signal multiple times while changing the specific frequency of the reference frequency signal,
The resonance frequency detection apparatus according to any one of claims 9 to 15, wherein the measurement unit detects a resonance frequency every time the measurement signal is generated a plurality of times.

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