JPH0767198B2 - Noise compensator for audio equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a noise compensator for an audio device that compensates for noise from being drowned out by a sound source, and more specifically, it will compensate for noise. The present invention relates to a noise compensation device for an audio device, which can avoid damage to a speaker even by noise compensation.

INDUSTRIAL APPLICABILITY The noise compensation device of the present invention is used for noise compensation of audio equipment mounted on a vehicle.

[Prior art and problems to be solved by the invention]

For example, so-called masking occurs in which sound from an audio device mounted on an automobile is drowned out mainly by low-frequency sounds of 100 Hz or less due to engine sound, operation sound of an air conditioner, and the like. For this reason, various measures have been taken to compensate for the noise masked by noise.

One of the conventional noise compensation means is to raise the volume level over the entire audible frequency band in order to counter the noise. However, this means not only makes the listener feel uncomfortable and uncomfortable, but also requires a high-output power amplifier for amplifying the audio signal, and a large-diameter speaker capable of high output even in the low frequency range. There is a problem of doing. On the other hand, a large-diameter speaker cannot be installed due to spatial restrictions in the interior of an automobile, and the speaker may be damaged if an excessive signal in the low frequency range is applied to the conventional speaker.

In order to solve the above-mentioned problem, there has been proposed a means for doubling the low-frequency sound range masked by noise and amplifying a signal of such double frequency to synthesize it with the original reproduced sound signal ( For example, a noise compensator for an audio device filed by the applicant of the present application (Japanese Patent Application No. 61-13294 (Japanese Patent Application Laid-Open No. 62-1294).
No. 71300)) "). This means uses the law that, even if the fundamental frequency is not heard, the listener feels the same feeling as when the fundamental frequency is heard, by hearing the sound of a frequency twice that of the fundamental frequency. In other words, by generating a sound with a frequency twice as high as the low frequency range masked by noise, even if the original low frequency range is masked by noise, the second-order overtone generated secondarily is reduced. It is intended to be heard by the listener as voice in the frequency range. According to this method, since only the masked low-frequency range is targeted, the above-mentioned problems such as the sense of discomfort in which the volume level increases overall, the need for a high-output power amplifier, and the need for a large-diameter speaker are solved to some extent. Has been done.

However, there is a problem in that the low temperature range is insufficient in hearing at a low volume by simply generating the second harmonic. In addition, since a low-frequency signal to be masked is also applied to the speaker, there is a problem that the speaker aperture cannot be made too small.

Therefore, there is a demand for a noise compensator that performs noise compensation while further improving sensitivity and sound quality. It is an object of the present invention to provide an improved noise compensator that fulfills this need. Further, it is desired to perform such noise compensation while reducing the aperture of the speaker, and a further object of the present invention is to improve the noise compensation by improving the sensitivity and sound quality while reducing the aperture of the speaker. It is to provide a device.

[Means for solving problems]

According to the present invention, a low-pass filter that passes only low-frequency components affected by noise in an original reproduction signal from an acoustic source, and a harmonic overtone generation circuit that generates a frequency signal that is an integral multiple of the frequency of the output signal of the low-pass filter A circuit that adjusts the level of the output signal of the overtone generation circuit in response to the noise level in the low frequency range, a circuit that corrects the loudness sensitivity of the output signal of the level adjustment circuit, and an output signal of the sensitivity correction circuit A circuit (6) for synthesizing (S5) and the original reproduction signal (S1) from the sound source, and causing a speaker to ring based on the output signal of the synthesizing circuit. A noise compensation device for an audio device is provided.

More preferably, a high-pass filter for blocking a low-frequency range frequency of the synthesized signal that has passed through the low-pass filter is further provided after the synthesis circuit, and a speaker is activated based on the output signal of the high-pass filter. A noise compensator for an audio device is provided.

[Work]

The low-frequency component to be masked by noise in the original reproduction signal from the acoustic source is extracted by a low-pass filter, and a signal having an integral multiple, preferably double frequency is generated. For example, even if the sound of the original low frequency component is masked by noise, the signal of this frequency becomes a compensating signal that the listener feels as the sound of the original low frequency component. The level of the compensation signal is adjusted according to the noise level in the low frequency range.

The bass sensitivity correction based on the loudness curve is performed on this level adjustment signal. This sensitivity correction improves the lack of bass at low volume. The bass sensitivity correction signal and the original reproduction signal are combined and the speaker is rung through the power amplifier.

More preferably, the low frequency range signal masked by noise in the synthesized signal is blocked so that it is not applied to the speaker. As a result, it is possible to reduce the diameter of the speaker and prevent the speaker from being damaged due to an excessive bass signal.

〔Example〕

A noise compensator for an audio device according to an embodiment of the present invention will be described with reference to the block diagram of FIG. In this embodiment, a case where the noise compensating device is applied to an on-vehicle audio device will be described.

In FIG. 1, a noise compensating device 100 includes a sound source 1 such as a CD.
The low-pass filter 2, the harmonic overtone generation circuit 3, the voltage control amplifier 4, the bass sensitivity correction circuit 5, the signal synthesis circuit, which inputs the original reproduction signal S1 from the device and outputs the signal S7 for causing the speaker 9 to ring through the power amplifier 8. 6 and a noise level response circuit 10.

The low-pass filter 2 is a low-frequency range to be masked by the original reproduction signal S1 (see FIG. 6 (a)) and noise (hatched portion in FIG. 6 (a)), 0 to 100 Hz in this embodiment. Pass the signal. Low pass filter 2
The low frequency signal S2 is applied to the overtone generation circuit 3. From an auditory sense, an overtone of an integral multiple of the fundamental frequency can be heard in the same manner as a sound of the fundamental frequency. However, in the present embodiment, the harmonic overtone generating circuit 3 outputs the double frequency signal S3 by the harmonizer shown in FIG. Is generated (Fig. 6 (b)).

In FIG. 2, the harmonizer includes a high-pass filter 31 that passes signals of 20 Hz or higher, a low-pass filter 32 that passes frequencies of less than 50 Hz, and a full-wave rectifier circuit 33 that distorts signals of 20 to 50 Hz selected by these filters. In the full-wave rectification circuit, a low-pass filter 34 that passes only a signal of less than 150 Hz among the signals whose frequency is an integral multiple, that is, a second harmonic is passed. The harmonizer also has a high-pass filter 35 that passes signals above 50 Hz, a low-pass filter 36 that passes signals below 100 Hz, a full-wave rectifier circuit 37 that generates an integer multiple frequency, and a low-pass filter 38 that passes signals below 200 Hz. Have. In this way, the double frequency audio signals extracted from both low pass filters 34 and 38 are mixed by the mixing circuit 39.

The double-frequency audio signal S3 from the harmonizer 3 is level-corrected according to the noise level (FIG. 6 (b)).
Such level correction is performed by the voltage control amplifier 4 and the noise level response circuit 10. As shown in FIG. 3, the noise level of the engine varies depending on the vehicle speed, and the noise level increases as the vehicle speed increases. Therefore, in the noise level response circuit 10, the output of the vehicle speed sensor (not shown) is input as the noise source signal SNZ, and the amplification factor α of the voltage control amplifier 4 is calculated according to the vehicle speed as shown in FIG. The voltage control amplifier 4 amplifies the amplitude of the signal whose frequency is doubled by the harmonizer 3 based on this amplification factor.

The output signal S4 of the voltage control amplifier 4 is applied to the bass sensitivity correction circuit 5. As shown in FIG. 5, the bass sensitivity correction circuit 5 includes a volume resistor 50, an amplifier 51, a feedback resistor 52 of the amplifier, a variable resistor 53 cooperating with the volume resistor, a resistor 54, and an inductance. It is composed of a series resonance circuit of 55 and capacitor 56, and a loudness curve is applied to the double frequency signal in response to the position of the volume resistor 50 to change the level increase amount (FIG. 6 (C)). This compensates for the lack of auditory bass when the volume is low.

As described above, the signal S5 having the doubled frequency, the noise level corrected, and the loudness sensitivity corrected is combined with the original sound reproduction signal S1 from the acoustic source 1 in the combining circuit (mixer) 6 (FIG. 6 (d)).

This combined signal S6 is directly applied to the speaker 9 via the power amplifier 8. From the speaker 9, S6 in FIG. 6 (d) =
A sound corresponding to S1 + S5 is generated, but the noise (NOISE) shown in FIG. 6 (a) masks the low frequency range as shown in the curve (V) of FIG. 6 (e). However, for the listener, the second harmonic overtones the curve CV2.
You can hear it as a voice like. In this case, since the overtones are loudness-sensitivity-corrected, the bass does not feel insufficient even when the volume is low. In the high range, the original reproduced sound is output.

In addition, since the level increase is applied only to the low frequency range,
It is not necessary to increase the size of the power amplifier 8.

A noise compensator as a second embodiment of the present invention will be described with reference to FIG.

The noise compensator shown in FIG. 7 has a high-pass filter 7 inserted and added between the synthesis circuit 6 and the power amplifier 8 of the noise compensator shown in FIG. The high-pass filter 7 blocks signals in the low frequency range masked by noise and outputs signals with frequency components higher than that to the power amplifier 8. That is, the bass sensitivity correction circuit 5 having a double frequency for noise compensation
Only a signal having a frequency equal to or higher than the frequency of the output signal S5 from is applied to the power amplifier 8. Also by this, the reproduced sound equivalent to that described with reference to FIG. 6 (e) can be obtained from the speaker 9.

On the other hand, since it is not necessary to apply a low frequency range signal erased by masking to the speaker 9, the speaker 9 does not need to operate in such a low frequency range. Therefore, the speaker 9 can be reduced in diameter. Further, since a low frequency excessive signal is not applied to the speaker 9, the possibility of damage is eliminated.

In FIGS. 1 and 7, the noise source signal SNZ of the noise level response circuit 10 may be added with an operation signal of the air conditioner or the like in addition to the vehicle speed to compensate for the noise of the air conditioner or the like.

〔The invention's effect〕

As described above, according to the first aspect of the invention, it is possible to realize noise compensation without causing insufficient bass even at a low volume.

According to the second aspect of the invention, the diameter of the speaker can be reduced, and the possibility that the speaker will be damaged can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a noise compensation device as one embodiment of the present invention, FIG. 2 is a harmonic overtone generation circuit diagram of FIG. 1, and FIGS. 3 and 4 are reproductions according to the noise level of FIG. FIG. 5 is a diagram for explaining the correction of the signal level, FIG. 5 is a bass sensitivity correction circuit diagram of FIG. 1, FIGS. 6 (a) to (e) are signal waveform diagrams showing the operation of the device of FIG. 1, and FIG. It is a block diagram of the noise compensation apparatus as another Example of this invention. (Description of symbols) 1 ... Sound source, 2 ... Low pass filter, 3 ... Overtone generation circuit (harmonizer), 4 ... Voltage control amplifier, 5 ... Bass sensitivity correction circuit, 6 ... Synthesis circuit (mixer) , 7 ... High-pass filter, 8 ... Power amplifier, 9 ... Speaker, 10 ... Noise level response circuit.

Claims (6)

[Claims] 1. A low-pass filter (2) for passing only low-frequency components affected by noise in an original reproduction signal (S1) from an acoustic source (1), and a frequency of an output signal (S2) of the low-pass filter. Overtone generation circuit (3) that generates a frequency signal of an integral multiple, circuits (4, 10) that adjust the level of the output signal of the overtone generation circuit in response to a low frequency noise level, and output of the level adjustment circuit A circuit (5) for correcting the loudness sensitivity of the signal, and a circuit (6) for synthesizing the output signal (S5) of the sensitivity correction circuit and the original reproduction signal (S1) from the acoustic source, A noise compensating device for an audio device, wherein a speaker is caused to ring based on an output signal of the synthesizing circuit. 2. The noise compensating apparatus for an audio device according to claim 1, wherein the harmonic overtone generating circuit includes a harmonizer for generating a doubled frequency. 3. The noise generated by an internal combustion engine of a vehicle is almost the same.
The noise compensating device for an audio device according to claim 2, which is a sound of 100 Hz or less. 4. A low-pass filter (2) for passing only a low-frequency component affected by noise in an original reproduction signal (S1) from an acoustic source (1), of a frequency of an output signal (S2) of the low-pass filter. Overtone generation circuit (3) that generates a frequency signal of an integral multiple, circuits (4, 10) that adjust the level of the output signal of the overtone generation circuit in response to a low frequency noise level, and output of the level adjustment circuit A circuit (5) for correcting the loudness sensitivity of the signal, a circuit (6) for combining the output signal (S5) of the sensitivity correction circuit and the original reproduction signal (S1) from the acoustic source, and the combining circuit ( A high-pass filter (7) for blocking frequencies in the low-frequency range that has passed through the low-pass filter of the combined signal output from 6) is provided, and a speaker is activated based on the output signal of the high-pass filter. Noise compensation apparatus for audio equipment, characterized and. 5. The noise compensating apparatus for an audio device according to claim 4, wherein the harmonic overtone generating circuit has a harmonizer for generating a doubled frequency. 6. The noise generated by an internal combustion engine of a vehicle is almost the same.
The noise compensator for an audio device according to claim 5, wherein the noise is a sound of 100 Hz or less.