JPH03106199A - Playback sound control device - Google Patents

Abstract

PURPOSE:To detect a noise level of a reproduced sound field accurately by controlling a sound signal reproduced from a speaker based on the comparison between a sound collection signal and a delayed sound signal. CONSTITUTION:There exists a delay by a time in response to a distance between, e.g. a speaker 1 and a sound collection microphone 2 till the reproduction sound from the speaker 1 is collected by the microphone 2. Then a sound signal obtained by delaying a sound signal outputted from the speaker 1 by a time requiring for the reproduced sound of the speaker 1 to be propagated to the microphone 2 and the sound collection signal collected by the microphone 2 are compared and the sound signal reproduced from the speaker 1 is controlled through the comparison. Thus, the reproduced sound is accurately controlled in response to the noise level of the reproduced sound.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a speaker for reproducing an acoustic signal, a microphone for collecting sound in a reproduction sound field, and a method for reproducing a sound from the speaker based on a sound signal collected by the microphone. The present invention relates to a reproduction sound control device including a control means for controlling an acoustic signal reproduced from a reproduction sound source.

[Conventional technology]

The above playback sound control device is used, for example, as a means to automatically control the volume of playback sound depending on the noise inside the cabin of a car. The sound signal was compared directly with the sound signal (for example, Japanese Patent Laid-Open No. 145714
(see Japanese Patent Application Laid-Open No. 178711/1983).

[Problem to be solved by the invention]

However, since the sound collection microphone simultaneously collects both the acoustic signal reproduced from the speaker and the noise inside the vehicle, it is difficult to collect the reproduced sound output to the speaker and the microphone. A configuration in which the sound signal is directly compared has the disadvantage that the control of the reproduced sound becomes inaccurate.

Therefore, it may be possible to remove the components of the reproduced sound output to the speakers from the collected sound signal, but in that case, simply removing the components of the reproduced sound output to the speakers from the collected sound signal will not solve the problem. The noise level inside the vehicle becomes inaccurate.

To explain, the speaker and the sound collection microphone are generally installed at separate locations.

Therefore, the sound reproduced from the speaker that is collected by the sound collection microphone has a time delay depending on the distance from the speaker, and the sound collected by the microphone and the acoustic signal output from the speaker are separated. Even if the comparison is made directly, the noise level of the reproduced sound field cannot be detected accurately.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to enable accurate detection of the noise level of a reproduced sound field.

[Means to solve the problem]

A reproduction sound control device according to the present invention includes a speaker for reproducing an acoustic signal, a microphone for collecting sound in a reproduction sound field, and controlling an acoustic signal reproduced from the speaker based on a signal collected by the microphone. It is equipped with a control means, and its characteristic configuration is as follows.

A first characteristic configuration is that a delay means is provided for delaying the acoustic signal output to the speaker by a time required for the sound reproduced by the speaker to propagate to the microphone or a time close to the time, and the control means The present invention is configured to control the acoustic signal reproduced from the speaker based on a comparison between the sound signal collected by the microphone and the acoustic signal delayed by the delay means.

A second characteristic configuration is that a propagation time detection means is provided for detecting the time required for the reproduced sound of the speaker to propagate to the microphone, and the delay means detects the time required for the reproduction sound of the speaker to propagate to the microphone, and the delay means detects the time required for the reproduction sound of the speaker to propagate to the microphone. It is configured to automatically adjust the delay time.

A third characteristic configuration is that a filter is provided for extracting a signal in a set frequency range from each of the acoustic signal output to the speaker and the sound signal collected by the microphone, and the control means is configured to control the filters. The present invention is configured to control an acoustic signal reproduced from the speaker based on a comparison of output signals.

[For production]

As described above, until the reproduced sound from the speaker is collected by the microphone, there is a delay corresponding to, for example, the distance between the speaker and the sound collection microphone.

Therefore, in the first characteristic configuration, the acoustic signal output to the speaker is compared with the acoustic signal delayed by the time required for the reproduced sound of the speaker to propagate to the microphone and the sound signal collected by the microphone. So do it.

However, it is better to set the delay time exactly to the time required for the sound played by the speaker to propagate to the microphone.
Although accurate control can be performed, the time may be set to be close to the time required for the reproduced sound from the speaker to be propagated to the microphone, thereby simplifying the device configuration.

By the way, it is difficult to accurately set the delay time, for example, numerically. Also, for example, in a vehicle-mounted audio system, speakers are installed on both the front and rear sides of the vehicle interior, and the volume of the reproduced sound from the front and rear sides can be changed and adjusted. In this case, the distance between the microphone and the virtual sound image position where the reproduced sound from each speaker is combined, that is, the actual propagation time of the reproduced sound to the microphone, changes depending on the volume difference between the front side and the rear side. The sound will be collected like this.

Therefore, in the second characteristic configuration, the time required for the reproduced sound from the speaker to be propagated to the microphone is detected, and the delay time of the delay means is automatically adjusted.

Furthermore, for example, most of the noise in the cabin of a car comes from vibration noise from the engine and running noise, so it is possible to extract only the noise in a specific frequency band where the fluctuations in the noise level are noticeable. Even when compared, the control accuracy of the reproduced sound does not deteriorate, and in fact, the device configuration can be simplified.

Therefore, in the third characteristic configuration, a filter is provided to extract a signal in a set frequency range from each of the acoustic signal output to the speaker and the sound signal collected by the microphone, and the output signals of these filters are Let them compare. However, the filter for the acoustic signal output to the speaker may act on either the delayed signal or the pre-delayed signal.

Note that the objects to be controlled by the control means include the volume, dynamic range, and frequency characteristics of the acoustic signal reproduced from the speaker, and as stated in claim 4, any one of these may be controlled. Alternatively, a plurality or all of them may be controlled.

By the way, when controlling the volume, the overall volume increases as the noise level of the playback sound field increases, and when controlling the dynamic range,
The volume of the reproduced sound in the low volume range is controlled so that the volume of the reproduced sound in the low volume range is increased as the noise level increases, and when controlling the frequency characteristics, for example,
In order to make the reproduced sound easier to hear, the volume of a specific frequency band of the acoustic signal output to the speaker is increased compared to other bands.

〔Effect of the invention〕

With the first characteristic configuration, it has become possible to accurately control the reproduced sound according to the noise level of the reproduced sound field.

In the second characteristic configuration, since the delay time of the acoustic signal output to the speaker can be automatically set, the adjustment of the device becomes easy.

In the third characteristic configuration, the device configuration can be simplified while comparing the sound reproduced by the speaker and the collected sound signal without reducing the accuracy.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, an embodiment in which the present invention is applied to a vehicle-mounted audio device will be described based on the drawings.

As shown in FIG. I, a pair of left and right speakers (1) for reproducing acoustic signals are provided in a rear location and a front location in the vehicle interior, respectively, and are configured in a so-called four-speaker type.

However, although not described in detail, the entire audio system will be installed inside the console panel at the front of the passenger compartment. An omnidirectional microphone (2) that collects sound from the reproduced sound field is installed on the operation panel surface of the acoustic device, and based on the sound signal collected by the microphone (2), The higher the noise level of the speaker (1), the higher the noise level of the speaker (1).
The volume of the playback sound is automatically adjusted so that the volume of the playback sound is increased.

To explain, the receiver, cassette I/deck, or C
Stereo audio signals output from various audio sources (3) such as a D player are input to a buffer amplifier (4) separately for each left and right channel.
The output signal of
The outputs of these voltage-controlled amplifiers (5) are sent to the main amplifier (7) via a fader (6) for adjusting the front and rear volume balance.
), and each of the front and rear speakers (L)
They are played from the beginning.

In other words, the voltage control amplifier (5) corresponds to a control means for controlling the sound reproduced by the speaker (1).

The signal collected by the microphone (2) is
The signal is amplified by a microphone amplifier (8) and input to a low-pass filter (9) that extracts a certain frequency of 100<

On the other hand, the output signal of the buffer amplifier (4) as an acoustic signal to be output to the speaker (1) is transmitted over the time required for the reproduced sound of the speaker (1) to be propagated to the microphone (2) or close to it. is delayed by a phase shifter (10) as a delay means for delaying the
The signal delayed by the phase shifter (■0) is input to a low-pass filter (l1) having the same characteristics as the low-pass filter (9), and is then input to a low-pass filter (11) having the same characteristics as the low-pass filter (9), The output signal is input to a subtracter (l2) to extract a noise signal corresponding to the noise level obtained by removing the component of the sound reproduced by the speaker (1) from the sound signal collected by the microphone (2). is detected by the voltage controlled amplifier (5) by the noise level detector (13).
) is converted into a DC voltage signal that serves as a control signal.

To explain the operation of the low-pass filters (9) and (11), the noise generated by the engine, which is the main noise source in the vehicle interior, is mostly composed of low frequency components of 1001 Hz or less, so the noise is 100 Hz or less. Even if the noise level is detected based on the level of the frequency component of the speaker (1), there is no risk that the accuracy will decrease.
It becomes possible to effectively remove frequency components such as reproduced sounds.

Therefore, the sound signal collected by the microphone (2) is manually applied to the low-pass filter (9) to remove the frequency components in the high frequency range.However, if the reproduced sound is a music signal, , the speaker (1
), signals with frequency components of 100 Hz or less are also reproduced.

As a result, the microphone (2) receives noise from the engine and IO output from the speaker (1).
Since both the reproduced sound and the reproduced sound with frequency components below OHZ are collected, the subtracter (12)
In order to be able to accurately remove reproduced sound with a certain frequency below 0k, the acoustic signal output from the buffer amplifier (4) delayed by the phase shifter (IO) is also filtered through the low-pass filter having the same characteristics. By passing (11), frequency components higher than 10 0 Hz are removed.

To explain the operation of the phase shifter (10), since the microphone (2) and the speaker (1) are installed at separate locations, the speaker that collects sound on the microphone (2) The reproduced sound from (1) is delayed in time from the time when it is output from the speaker (1).

Therefore, if the output signal of the buffer amplifier (4) is directly subtracted from the sound collection signal of the microphone (2), the control signal output from the subtracter (12) will not accurately correspond to the noise level. It doesn't matter.

Therefore, the output signal of the buffer amplifier (4) is input to the phase shifter (10) as a delay means to delay the time required for the sound reproduced by the speaker (1) to propagate to the microphone (2). After that, a low-pass filter <9> passes the collected sound signal of the microphone (2>).
) is compared with the output signal of ).

In addition, the microphone (2) and the speaker (1)
), once installed, their positional relationship does not change, but the playback volume from the speaker (1) may be adjusted to different values at the front and rear by the fader (6).

In other words, when the fader (6) is operated, the volume ratio of the reproduced sound from both the front and rear speakers (1) changes, and the virtual sound image position where the reproduced sounds from the front and rear speakers (1) are combined, that is, the microphone ( 2) The time during which the reproduced sound propagates changes depending on the operating position of the fader (6).

Furthermore, when the power is turned on, the position of the fader (6) is unknown.

Therefore, when the device is started for the first time when the power is turned on, and when the fader (6) is operated to a different position from the current position, the while outputting a marker sound for propagation time measurement from the speaker (1) instead of the reproduced sound,
Propagation time detection means (14) for detecting the time required for the reproduced sound from the speaker (1) to propagate to the microphone (2) is provided, and the delay time by the phase shifter (10) is automatically adjusted. It is set as.

To explain further, an oscillator (15) with a 75-wire oscillation frequency that falls within the passband of each of the 100 I{z low-pass filters (9) and (11), and the microphone amplifier (8).
a 75-cell bandpass filter (16) that passes only the oscillation frequency component of the oscillator (15) from the output signal of the oscillator (15) and the acoustic signal input to the phase shifter (10);
(17) and their bandpass filters (16),
(17) for phase comparison as a propagation time detection means for detecting a phase difference between the output signals, that is, a signal corresponding to the time required for the reproduced sound from the speaker (1) to propagate to the microphone (2). AND circuit (18),
an 8-integrator (l9) that converts the output signal of the AND circuit (l8) into a DC voltage signal corresponding to the phase difference;
Based on the output level of the integrator (19), the phase shift amount by the phase shifter (10) is set to phase shift angles (60 degrees, 120 degrees, and 180 degrees) corresponding to three stages of large and small delay times. three comparators (20) to switch to
and three flip-flops (2) to maintain the output state of these comparators (20) even after the marker signal disappears, and the phase shift angle or delay of the phase shifter (IO) is time, both low-pass filters (
9) and (11) are automatically adjusted so that the difference between the output signals is minimized.

In the figure, (22) is a marker sound detector that detects that the marker signal from the oscillator (15) is reproduced from the speaker (1), and (23) is the marker sound detector (22). Based on the output of the three comparators (
20) and a switch circuit for operating the three flip-flops (2l) to reset the delay time of the phase shifter (10); (24) detects the turning on of the power switch (25); (26) is a one-shot multi-by-break that uses a comparator to output a pulse signal for outputting the marker sound for a set time; This is a one-shot multi-by break that uses a comparator to output a pulse signal similar to the one-shot multi-by break for detection, and includes a potentiometer (
27) is configured to detect the presence or absence of a voltage change.

(28) is the comparator (2) for detecting power-on.
4) output and a comparator for detecting the fader operation (
An OR circuit (29) for combining the output of the OR circuit (28) with the output of the sound source (3) and the output of the sound source (3). This is a switch circuit for switching between the marker signal and the marker signal.

[Another example]

In the above embodiment, the phase shifter (10) is used as the delay means, but a shift register, memory, etc. may be used for delay, and the specific configuration of the delay means can be changed in various ways.

Further, in the above embodiment, the delay time of the delay means is exemplified as being adjusted in three stages, but it may be possible to adjust it continuously.

Further, in the above embodiment, a case where the delay time is automatically adjusted is illustrated, but it may be simplified and implemented so that the delay time is manually set.

Further, in the above embodiment, the volume of the reproduced sound is automatically adjusted as a control target, but for example, as shown in FIG. 2, the frequency characteristics and dynamic range of the reproduced sound may be controlled. You can.

To explain, when controlling the frequency characteristics, auditory sensation correction may be performed such that the higher the noise level, the more the low-frequency components and high-frequency components of the reproduced sound are enhanced. In addition, when controlling the dynamic range, auditory perception correction may be performed such that as the noise level increases, signals in a small volume range are emphasized to some extent with respect to signals in a high volume range.

In Fig. 2, (30) is a preamplifier for switching the audio signal of the audio source (3) and adjusting the sound quality;
1) is a frequency characteristic control device, (32) is a compressor for dynamic range control, and (33) is a frequency characteristic control device, (33) is a frequency characteristic control device, and (33) is a frequency characteristic control device, and (33) is a frequency characteristic control device, and (33) is a frequency characteristic control device, and (33) is a frequency characteristic control device, and (33) is a frequency characteristic control device. A controller using a microcomputer, which constitutes a control means for controlling the operation of each of the frequency characteristic control device (31), the compressor (32), and the gain control section having the same function as the voltage control amplifier (5); 34) is the output of the noise level detector (13) that integrates the output of the subtracter (12) input to the controller (33) and converts it into a DC voltage according to the noise level, and the output of the preamplifier (30). This is an A/D converter for converting signals into digital values.

Furthermore, in the above embodiment, the speaker (1) is provided at the front and rear of the vehicle interior, but it may also be provided only at the front or rear, and the number of speakers (1) and microphones (2) installed and the The specific configuration of the installation location can be changed in various ways.

Furthermore, in the above embodiment, the case where the present invention is applied to an in-vehicle audio device is illustrated, but the present invention can be applied to various types of audio devices. It can also be used as a means for controlling the reproduced sound according to the noise level at the work site in a loudspeaker device for transmitting information.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of drawings]

The drawings show an embodiment of a reproduction sound control device according to the present invention, with FIG. 1 being a block diagram of a control configuration, and FIG. 2 being a block diagram showing a control configuration of another embodiment. (l)...Speaker, . (2)・・・・・・
Microphone, (5)... Control means, (9)
, (11)... Filter, (10)...
... Delay means, (l4) ... Propagation time detection means.

Claims (1)

[Scope of Claims] 1. A speaker (1) for reproducing an acoustic signal, a microphone (2) for collecting sound with respect to the reproduction sound field, and a speaker ( 1) control means (
5), the reproduction sound control device comprising: an acoustic signal to be output to the speaker (1);
A delay means (10) is provided for delaying the time required for the reproduced sound to be propagated to the microphone (2) or a time close thereto, and the control means (5) controls the sound collected by the microphone (1). A reproduced sound control device configured to control an acoustic signal reproduced from the speaker (1) based on a comparison between a collected sound signal and an acoustic signal delayed by the delay means (10). 2. The reproduced sound control device according to claim 1, further comprising propagation time detection means (1) for detecting the time required for the reproduced sound of the speaker (1) to be propagated to the microphone (2).
4), wherein the delay means (10) is configured to automatically adjust its delay time based on the detection information of the propagation time detection means (14). 3. The reproduced sound control device according to claim 1 or 2, wherein the reproduction sound control device includes a sound signal outputted from the speaker (1) and a sound signal collected by the microphone (2). Filters (9) and (11) for extracting signals in a set frequency range are provided, and the control means (5)
A reproduction sound control device configured to control an acoustic signal reproduced from the speaker (1) based on a comparison of output signals of both the filters (9) and (11). 4. The reproduction sound control device according to any one of claims 1 to 3, wherein the control means (5) is configured to control the speaker (
1) A playback sound control device configured to control at least one of the volume, dynamic range, and frequency characteristics of the sound signal played back.