JPS6158049B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic correction device for a comprehensive sound transmission characteristic that combines the transmission characteristics of a sound reproduction device and a sound field.

Conventionally, when automatically correcting the acoustic transmission characteristics of a sound field including sound reproduction equipment, a specific audio signal for adjustment is emitted into the sound field, received by a microphone, etc., and a graphic equalizer is used. frequency characteristics were automatically changed. FIG. 1 shows an automatic sound field correction device that the applicant is considering. first,
A pink noise generator 1 is connected to a graphic equalizer 2 whose amplitude frequency characteristics are set flat in advance.
Pink noise is added, amplified by an amplifier 3, and applied to a speaker 5 in a listening room 4. The acoustic transmission characteristics of the speaker 5 and the sound field combined are collected by the microphone ₆ , frequency-analyzed by the band-pass filters 7 ₁ . 8n, and the results are converted into digital signals by AD converters 9 ₁ . . . 9n and applied to the digital arithmetic processing unit 10.
On the other hand, the circuit configuration is such that the level of each resonance point of the graphic equalizer 2 can be controlled by the digital arithmetic processing unit 10. It is assumed that the digital processing unit 10 has a function of controlling the level of each resonance point of the graphic equalizer 2 so that the result of the band frequency analysis becomes a desired frequency characteristic. Furthermore, the graphic equalizer 2 has a band pass filter or a band elimination filter for each frequency band, and performs correction by integrating the characteristics of each of these filters.
The gain at a certain resonance point is influenced by the frequency characteristics of other resonance points. Therefore, even if you specify the gain at each resonance point of the graphic equalizer based on the results measured by band frequency analysis, it is not necessary to correct it at once so that the acoustic transmission characteristics have the desired frequency characteristics. I can't. Therefore, it is necessary to provide feedback to the control code by repeating the correction process. That is, pink noise is again added to the graphic equalizer to which the control code has been applied, and the acoustic transmission characteristics are measured. The control code is again specified in a direction that compensates for the difference between this result and the desired frequency characteristic.

By repeating the above steps, it is possible to realize correction characteristics that take into account the influence of frequency characteristics other than the center frequency of each resonance point.

Here, the control code is given by an address code and a data code, and it is necessary to convert the binary code specified by the address code into a decimal code and select the resonance point of the graphic equalizer.

The bandpass filters 7 ₁ ... 7n are composed of a plurality of filters each having a band corresponding to each resonance point of the graphic equalizer 2,
Also, a plurality of detectors 8 and a plurality of A-D converters 9 are required, but for example, if the bandpass filter is made variable in band and sweeps over the entire range, one can be used.
Accordingly, only one detector 8 and one AD converter 9 are required.

If the bandpass filter 7 is composed of a plurality of filters, a switch for sequential selection is inserted between the bandpass filter 7 and the detector 8 or between the detector 8 and the A/D converter 9. In this way, only one detector 8 and one AD converter 9 or AD converter 9 are required.

In the embodiment of the automatic sound field correction device described above, the bandpass filter 7 is arranged after the microphone 6, but the invention is not limited to this, and for example, the pink noise generator 1
It is placed in the rear stage, that is, in the front stage of the graphic equalizer 2, and sequentially changes the band pass over the entire band.
In other words, it is a matter of course that it may be swept.
Here, if adjustment cannot be made with one sweep,
Because it will be swept over and over again,
Band noise that is repeatedly swept over the entire listening room 4 will be emitted, but it is easier to hear than when pink noise is emitted for a long time as shown in Figure 1, so automatic adjustment is performed. It can relieve the pain of being drowned.

Further, in order to generate the above-mentioned pink noise or band noise, a disc record or the like on which pink noise or band noise is recorded in advance may be used. An example of a frequency characteristic adjustment circuit used to obtain a graphic equalizer 2 capable of controlling the level of each resonance point is shown in FIGS. 2 and 3. T ₁ (s) to T _o (s) in the figure are bandpass filters and have the following transfer function.

Ti(s)=Δωi S/S ² +Δωi S+ω ²
i Here, Δωi is the half width of the resonance point, and ωi is the resonance angular frequency. Further, if the angular frequency is ω, then S=jω. Note that the transfer function of the graphic equalizer shown in FIGS. 2 and 3 is expressed by the following equation.

An example of a graphic equalizer 2 obtained by adding a control circuit to the frequency characteristic adjustment circuit described above is shown in FIGS. 4 and 5. In the figure, in the control code, that is, the address code and data code sent out from the digital arithmetic processing unit 10, the address code 22 is transferred to the BCD-TEZIMAL decoder 2.
1, the data code 23 input to the D-A converter _{15 1} .
...16n generates a latch pulse to latch the data code 23. One bit of the data code 23 is applied to FET switches 19 _{1 .} . . 19 n which determine whether the resonance point is in a peak state or a dip state.

When automatically adjusting a plurality of graphic equalizers, such as for stereo, in the above automatic sound field correction apparatus, the graphic equalizers of other available channels can be used as band-pass filters. An example of this case is shown in FIG. In the figure, graphic equalizers 33 and 34 are for the left channel and right channel of stereo, respectively. First, pink noise is added to the left graphic equalizer 33, whose amplitude frequency characteristics have been set flat in advance, and is amplified to create a sound inside the listening room. is added to the speaker 5 of. The combined sound transmission characteristics of the speaker and the sound field are collected by the microphone 6 and added to the right graphic equalizer 34. By setting the gain of one of the resonance points of the right-hand graphic equalizer 34 constant and setting the other gains to zero, it is used as a bandpass filter, and the digital processing unit 10 sequentially switches the resonance points, and by taking in the data, the frequency Perform analysis.

Although the resonance characteristics of a graphic equalizer are different from the frequency characteristics of a bandpass filter, they can be approximately substituted.

In the above example, only the level of the resonance point is controlled using a DA converter, but the resonance angular frequency ωi, half-width Δωi or sharpness Q of the bandpass filter Ti(s) is controlled by D- It is also possible to control using an A converter.

Furthermore, the digital calculation processing shown in FIG. 1 can be performed using a microcomputer or the like. In addition, the detector and A-
It is convenient to provide a logarithmic amplifier between the D converters, since digital calculations can be performed in decibels.

FIG. 7 shows another automatic sound field correction device considered by the applicant, in which the same parts as in FIG. The sound is then added to the speaker 5 in the listening room 4 via the amplifier 3, emitted, and captured by the microphone 6. The output of microphone 6 is graphic equalizer 2.
The signals are applied to detectors 8 _{1 .} . . 8n through bandpass _{filters 7} 1 . The outputs of the comparators 41 ₁ . . . 41 n are respectively applied to up-down counters 42 ₁ . The reference voltage of the comparator is the reference voltage generator 4.
3 ₁ ... given by 43n.

In the above configuration, the pink noise emitted into the sound field via the graphic equalizer 2 to be controlled is affected by the overall acoustic transmission, is frequency-analyzed by the band-pass filters ₇₁ ...7n, and is then passed through the detector. 8 ₁ ... 8n and compared with the reference voltage set by the reference voltage generators 43 ₁ ... 43n, and if the output of each detector 8 ₁ ... 8n is higher than the reference voltage, the corresponding comparator The output becomes high level and puts the next stage counter in down mode. Since this count counts down the external clock, the control code to the DA converter that controls the level of the corresponding resonance point of the graphic equalizer 2 gradually becomes smaller in value, causing a dip characteristic at the resonance point. This operation is performed until the detected output becomes equal to the reference voltage, and the correction is completed. Further, when the detection output is lower than the reference voltage, the corresponding up-down counter is put into the up mode and operates in the opposite manner. In the above manner, correction is automatically performed.

However, when using the automatic sound field correction device as described above, sound is emitted within the listening room while the correction is being performed, which causes pain during measurement.

The present invention has been made to improve these drawbacks, and will be described in detail below with reference to Examples. FIG. 8 shows an embodiment of the present invention capable of alleviating such pain, in which the output of the pink noise generator 1 is connected to the normally closed contact of the switch 45. A movable contact of switch 45 is connected to graphic equalizer 2, and its output is connected to a movable contact of switch 47. switch 47
The normally closed contacts of are connected to the speakers 5 of the listening room 4 via the amplifier 3, the normally open contacts are connected to the band pass filters 7 ₁ to 7n, and the detectors 8 ₁ to 8n and the comparators 41 ₁ to 41n as described above. ,
The graphic equalizer 2 is controlled via up-down counters 42 ₁ to 42 n. switch 46
The normally closed contact is connected to the output terminal of the microphone 6, and the normally open contact and the movable contact are connected to the output terminal and input terminal of the delay memory element (BBD, CCD, etc.) 44, respectively. Also, the normally open contacts of switches 45 and 46 are connected.

In the above configuration, it is assumed that each switch is initially folded down to the normally closed contact side as shown in the figure, and that the graphic equalizer 2 has a flat characteristic, so that pink noise is emitted into the listening room as described above. The pink noise that has been affected by the characteristics within the listening room 4 is stored in the delay storage element 44. When the storage is completed, the switches 45, 46 and 47 are set to the normally open contact side, so that the stored pink noise continues to be sent to the graphic equalizer 2 at all times while the stored contents circulate within the delay storage element 44. Then, graphic equalizer 2 → bandpass filter 7 → detector 8 →
Comparator 41 → Up-down counter 42 →
The graphic equalizer 2 is controlled through the path of the graphic equalizer 2 until the pink noise stored as described above, that is, the pink noise affected in the listening room, is corrected to be the same as the original pink noise. In this case, by adjusting the reference voltages 43 _{1 .} . . 43n corresponding to each resonance point, it is possible to obtain not only a flat frequency characteristic but also a desired frequency characteristic. In this case, the pink noise is emitted into the listening room 4 only until it is stored in the delay memory element, so it is extremely short-term and causes less pain to the listener.

As described above, according to the present invention, the characteristics of the graphic equalizer can be automatically corrected to match the acoustic transmission characteristics of the sound field including the audio reproduction equipment, and in this case, the supply time of the audio signal for adjustment can be adjusted automatically. It is possible to obtain an excellent effect of extremely reducing the amount of

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional example, FIGS. 2 and 3 are circuit diagrams showing a part of a graphic equalizer used in the present invention, and FIGS. 4 and 5 are circuit diagrams showing a part of a graphic equalizer used in the present invention. A block diagram showing an example, FIGS. 6 and 7 are conventional examples, and FIG. 8 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 is a pink noise generator, 2 is a graphic equalizer, 4 is a listening room, and 7 ₁ ...
7n is a band pass filter, 1 is a digital arithmetic processing unit, 42 ₁ . . . 42n is an up/down counter, and 44 is a delay storage element.

Claims (1)

[Claims] 1 means for selectively adding either the audio signal output or the output of the delay storage circuit to the graphical equalizer by a first selection means; and a second selection means for selecting the output of the graphical equalizer as either the speaker or the frequency analysis means. automatic control means for controlling the graphic equalizer according to the output of the frequency analysis means; detection means for detecting the acoustic output from the speaker; means for selectively adding either the output of the delay storage circuit or the output of the detection means by the selection means, and when the first selection means selects the audio signal output, the second and third The selection means respectively select the output of the speaker and the detection means, and when the first selection means selects the output of the delay storage circuit, the second and third selection means respectively select the output of the frequency analysis. An automatic sound field correction device characterized in that each of the selection means is linked to select the output of the delay storage circuit and the delay storage circuit.