JP5151941B2 - Sound equipment - Google Patents

Description

  The present invention relates to an acoustic device that prevents howling.

  Various methods have been proposed for suppressing howling generated by collecting sound emitted from a speaker of its own device with a microphone in an acoustic device (see, for example, Patent Document 1).

In the audio signal amplification circuit described in Patent Document 1, when howling is detected, a low-pass filter for removing howling is operated to lower the gain of the audio signal amplification circuit. The audio signal amplifier circuit checks whether or not howling is detected by stopping the operation of the low-pass filter at predetermined intervals. The audio signal amplification circuit gradually decreases the gain until no howling is detected. In the audio signal amplifier circuit, the howling is fixed to a gain that is no longer detected.
Japanese Patent Laid-Open No. 7-15788

  Normally, when the positional relationship between the speaker and the microphone changes, the sound transmission system changes, and thus the loop gain changes. That is, the loop gain threshold at which howling occurs is not uniquely determined. For this reason, it is usually necessary to reduce the gain of various devices in the closed loop with a certain margin. Therefore, the present invention provides an acoustic device that adjusts to an optimum loop gain according to changes in the environment.

  The acoustic device of the present invention includes a speaker and a microphone, and is, for example, a PA system. When detecting the occurrence of howling, the acoustic device stores the measured distance from the speaker to the microphone and the estimated loop gain at that time in association with each other. The acoustic device considers that howling will occur when the estimated loop gain approaches the loop gain associated with the distance from the speaker to the microphone, for example, lowers the gain of the acoustic device or displays a warning message. To do.

  Thereby, even if the positional relationship between the speaker and the microphone is changed (that is, even when the environment is changed), the acoustic device can be adjusted to an optimum loop gain according to the change in the environment.

  Moreover, the acoustic device according to the present invention may include a display unit (for example, a monitor) that displays various images. The acoustic device stores distances between a plurality of speakers in advance, and calculates a microphone position based on the distance between the speakers and the measured distance between the speaker and the microphone. The acoustic device displays the positional relationship between the plurality of speakers and microphones and the loop gain for each microphone position.

  Thereby, the acoustic device can display a plurality of speakers and microphone positions, and can display an optimum loop gain for each microphone position. For this reason, the user can know at a glance where the feedback is likely to occur.

  Furthermore, the acoustic device stores the distance from the speaker to the microphone and the default value of the loop gain in association with each other, and updates and registers the estimated loop gain when a predetermined time elapses. It is good also as a structure which returns a gain to a default value.

  As a result, even when the loop gain serving as the threshold is too low and the sound output volume is too low, it can be restored to the default value after a predetermined time has elapsed, so that no sound can be prevented from being produced.

  The acoustic device of the present invention can be adjusted to an optimal loop gain according to the environment.

  An acoustic device 1 according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of an environment in which an audio device is installed. FIG. 2 is a block diagram illustrating the function and configuration of the acoustic device. FIG. 3 schematically shows the time axis characteristics of an audio signal input to the microphone. FIG. 4 is a diagram illustrating an example of the gain table.

  As shown in FIG. 1, the acoustic device 1 is installed in a living room 4 and includes two speakers SP1, a speaker SP2, and one microphone MIC. The two speakers SP1 and SP2 are fixedly installed in the living room 4, and the microphone MIC can be carried by the user. Hereinafter, the distance from the speaker SP1 to the microphone MIC is D1, and the distance from the speaker SP2 to the microphone MIC is D2. The number of speakers and microphones may be one or more.

  As shown in FIG. 2, the acoustic device 1 includes a microphone MIC, an LPF unit 11, a gain adjustment unit 12, a speaker SP1, a speaker SP2, an addition unit 25, a howling detection unit 26, a storage unit 27, a control unit 28, and a display unit. 29. Furthermore, the acoustic device 1 includes a signal generation unit 13A, an HPF unit 14A, a superposition unit 15A, an HPF unit 21A, a correlation unit 22A, a distance measurement unit 23A, and a gain estimation unit 24A on the channel A. The acoustic device 1 includes a signal generator 13B, an HPF unit 14B, a superimposing unit 15B, an HPF unit 21B, a correlation unit 22B, a distance measuring unit 23B, and a gain estimating unit 24B in the channel B. Hereinafter, with regard to the functions and configurations provided for the channels, the signal generator 13A, HPF unit 14A, superimposing unit 15A, speaker SP1, HPF unit 21A, correlation unit 22A, distance measuring unit 23A, and gain estimating unit 24A are examples. Will be described.

  The microphone MIC collects surrounding sounds including the user's uttered voice and generates a voice signal. The microphone MIC outputs the generated audio signal to the LPF unit 11, the HPF unit 21A, the HPF unit 21B, and the howling detection unit 26.

  When an audio signal is input from the microphone MIC, the LPF unit 11 passes only an audio signal having a frequency less than a predetermined frequency band (for example, less than 20 kHz) so as not to loop a PN code, which will be described later, to the gain adjusting unit 12. Output. The LPF unit 11 is not an essential configuration.

  The gain adjustment unit 12 adjusts the gain of the audio signal input from the LPF unit 11 based on an instruction from the control unit 28 described later. The gain adjusting unit 12 outputs the audio signal after gain adjustment to the superimposing unit 15A and the superimposing unit 15B.

  The signal generation unit 13A periodically generates a PN code (M sequence) with high autocorrelation as pseudo noise. The signal generation unit 13A outputs the PN code to the HPF unit 14A and the correlation unit 22A, and outputs the generation timing of the PN code to the distance measurement unit 23A. Further, the signal generator 13A and the signal generator 13B output PN codes having different patterns. In addition, you may use other random numbers, such as not only M series but Gold series. In particular, when using a Gold sequence PN code, it is possible to generate a large number of types of code sequences by switching the tap position of a code generation circuit (shift register), so that it is compatible with a large-scale PA system. be able to. The signal level of the PN code may be a weak level that does not cause a sense of incongruity, but a level that can detect a correlation peak of the PN code (hereinafter referred to as a correlation peak) is secured.

  When the PN code is input from the signal generation unit 13A, the HPF unit 14A passes only the PN code in a frequency band (for example, 20 kHz or more) that is difficult for the user to hear, and outputs the PN code to the superposition unit 15A. The HPF unit 14A is not an essential configuration in the present invention. However, since the HPF unit 14A cuts the sound other than the high range of the PN code, even if the sound is emitted from the speaker SP1, there is no sense of incongruity in hearing (noise is difficult to hear).

  The superimposing unit 15A generates a synthesized signal by superimposing the PN code from the HPF unit 14A on the audio signal from the gain adjusting unit 12, and outputs the synthesized signal to the speaker SP1.

  The speaker SP1 emits sound based on the synthesized signal input from the superimposing unit 15A. The sound emitted from the speaker SP1 is collected by the microphone MIC, and a closed loop is formed by the microphone MIC, the LPF unit 11, the gain adjusting unit 12, the superimposing unit 15A, and the speaker SP1.

  When an audio signal is input from the microphone MIC, the HPF unit 21A passes only an audio signal in a frequency band (for example, 20 kHz or more) in which a PN code exists and outputs the audio signal to the correlation unit 22A.

  The correlation unit 22A obtains the correlation between the audio signal input from the HPF unit 21A (the PN code is included in the audio signal collected by the microphone MIC) and the PN code input from the signal generation unit 13A. Since the PN code has a very high autocorrelation, if the same PN code is included in the voice signal input from the HPF unit 21A, a sharp correlation peak (a predetermined threshold value or more) is periodically generated. Correlation peaks with levels of The correlation unit 22A outputs the timing at which the correlation peak is calculated to the distance measurement unit 23A, and outputs the correlation value when the correlation peak is calculated to the gain estimation unit 24A.

  The distance measurement unit 23A receives the distance D1 from the speaker SP1 to the microphone MIC based on the time difference T from the input of the PN code generation timing from the signal generation unit 13A to the timing at which the correlation peak is calculated by the correlation unit 22A. Is calculated. The distance D1 can be calculated by multiplying the sound speed C and the time difference T. The distance measuring unit 23A outputs the calculated distance D1 to the control unit 28.

  The gain estimation unit 24A estimates the loop gain based on the correlation value, and outputs the estimated loop gain to the addition unit 25. Specifically, as shown in FIG. 3, the gain estimation unit 24A obtains the absolute value | A | of the correlation peak detected first after outputting the PN code. The waveform around the timing at which the first correlation peak is detected can be regarded as a direct sound (direct wave) returned to the microphone MIC. For example, the gain estimation unit 24 estimates the absolute value | A | as a loop gain.

  Specifically, the gain estimation unit 24A acquires a correlation peak that appears before a predetermined time elapses from the first correlation peak (that is, until the signal generation unit 13A outputs the next PN code). The gain estimation unit 24A selects an absolute value | A |, an absolute value | B |, and an absolute value | C | of a correlation peak at a predetermined level L or higher among the acquired correlation peaks. The delay time of the spatial sound emission system from the speaker SP1 to the microphone MIC is longer than the delay time of the signal processing system from the microphone MIC to the speaker SP1. For this reason, the waveform until a predetermined time elapses from the first correlation peak can be determined as a reflected wave such as a wall. The gain estimation unit 24A estimates | A | + | B | + | C | as a loop gain as a result of integrating the absolute values of the correlation peaks of the direct wave and the reflected wave.

  Adder 25 adds the loop gains input from gain estimator 24A and gain estimator 24B, and outputs the result to controller 28 as the gain of the closed loop of the microphone MIC system.

  When a sound signal is input from the microphone MIC, the howling detection unit 26 detects whether howling has occurred. For example, the howling detection unit 26 measures the level of each frequency component of the input audio signal, detects the presence / absence of an unnaturally large level frequency component as compared with other frequency components, and continues for a predetermined time or more. If this is detected, it is detected that howling has occurred. The howling detection unit 26 outputs a control signal indicating that howling is occurring to the control unit 28 while detecting howling.

  The storage unit 27 stores a gain table 271 shown in FIG. In the gain table 271, a distance D1 from the speaker SP1 to the microphone MIC and a distance D2 from the speaker SP2 to the microphone MIC are registered in association with the closed loop gain.

  Further, in the gain table 271, default values of closed-loop gains are registered in advance in association with the distances D1 and D2. As this default value, a loop gain input by a user operation or a loop gain measured in advance is used.

  When the control signal is input from the howling detection unit 26, the control unit 28 uses the loop gains registered in association with the distance D1 and the distance D2 input from the distance measurement unit 23A and the distance measurement unit 23B as gains. Obtained from the table 271. At this time, when the loop gain input from the adding unit 25 is smaller than the threshold value, the control unit 28 updates and registers the loop gain in the gain table 271 in association with the distance D1 and the distance D2. And the control part 28 starts a timer. When a predetermined time (for example, the time required for one performance, the time required for one song, etc.) has elapsed since the start of a built-in timer (not shown), the control unit 28 returns the loop gain that has been registered to the default value. The control unit 28 may gradually return the loop gain to the default value so that the loop gain returns to the default value when a predetermined time has elapsed. In this case, the audio device 1 can return the loop gain to the default value without any sense of incongruity in hearing.

  When the distance D1 and the distance D2 are input from the distance measurement unit 23A and the distance measurement unit 23B, the control unit 28 acquires, from the gain table 271 as a threshold, the loop gain associated with the distance D1 and the distance D2. To do. When the closed-loop gain input from the adding unit 25 approaches the threshold value, the control unit 28 regards that howling occurs, and instructs the gain adjusting unit 12 to decrease the gain. Further, the control unit 28 displays a warning message “howling occurs” on the display unit 29 which is a monitor. Note that the control unit 28 may instruct both gain adjustment and warning message display, or may instruct only one of them.

  As described above, the acoustic device 1 stores the loop gain threshold at which howling occurs according to the distance between the speaker SP1, the speaker SP2, and the microphone MIC. Therefore, the acoustic device 1 can set an optimum loop gain according to the positional relationship between the speaker SP1, the speaker SP2, and the microphone MIC (according to a change in environment).

  When a plurality of speakers are provided, the gain map shown in FIG. FIG. 5 is a diagram illustrating an example of the gain map. In this case, the acoustic device 1 displays the positional relationship among the speaker SP1, the speaker SP2, and the microphone MIC, and displays the loop gain stored in the gain table 271 for each position of the microphone MIC. Specifically, the storage unit 27 stores a distance DS between the speaker SP1 and the speaker SP2 in addition to the gain table 271. The distance DS may be a preset value or may be registered by a user operation input. The control unit 28 fixes the speakers SP1 and SP2 with a distance DS apart. The control unit 28 calculates the position of the microphone MIC using triangulation based on the distance DS and the distances D1 and D2 registered in the gain table 271. Then, the control unit 28 displays the loop gain associated with the distance D1 and the distance D2 at that time in association with the position of the microphone MIC. At this time, the control unit 28 may display a loop gain by giving a certain area to the position of the microphone MIC. For example, the control unit 28 divides the living room 4 into a plurality of areas, and sets a plurality of areas around the device itself. The control unit 28 determines to which region the calculated position of the microphone MIC corresponds to the division of the living room 4, and sets the loop gain associated with the distance D1 and the distance D2 used for the calculation to the corresponding region. assign. The control unit 28 generates a gain map by performing the above-described processing on all data registered in the gain table 271. Further, when the position of the microphone MIC based on other data corresponds to the area corresponding to the position of the microphone MIC based on the data registered in the gain table 271, the control unit 28 is small in these data. Assign a loop gain to the area.

  The acoustic device 1 may store a gain table 272 shown in FIG. 6 instead of the gain table 271. FIG. 6 is a diagram illustrating an example of another gain table. The gain table 272 stores, for each region, a loop gain threshold value that is considered to be howling. In this case, the control unit 28 calculates the position of the microphone MIC based on the distance DS and the measured distances D1 and D2, determines which region the calculated microphone MIC position corresponds to, and sets a threshold value. Get or register for updates.

It is a figure which shows an example of the environment which has installed the audio equipment. It is a block diagram which shows the function and structure of an audio equipment. This is a schematic representation of the time axis characteristics of an audio signal input to a microphone. It is a figure which shows an example of a gain table. It is a figure which shows an example of a gain map. It is a figure which shows an example of another gain table.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Acoustic apparatus, 11 ... LPF part, 12 ... Gain adjustment part, 13A, 13B ... Signal generation part, 14A, 14B ... HPF part, 15A, 15B ... Superimposition part, 21A, 21B ... HPF part, 22A, 22B ... Correlation , 23A, 23B ... distance measurement unit, 24A, 24B ... gain estimation unit, 25 ... addition unit, 26 ... howling detection unit, 27 ... storage unit, 271, 272 ... gain table, 28 ... control unit, 29 ... display unit , 4 ... Living room, C ... Sound velocity, D1, D2, DS ... Distance, MIC ... Microphone, SP1, SP2 ... Speaker

Claims (3)

An audio device including a speaker and a microphone,
Detection means for detecting occurrence of howling;
Distance measuring means for measuring the distance from the speaker to the microphone;
Gain estimating means for estimating a loop gain;
Storage means for storing a distance from the speaker to the microphone and a loop gain in association with each other;
When the detection means detects the occurrence of howling, the distance measured by the distance measurement means at that time and the loop gain estimated by the gain estimation means are associated with each other and updated and registered in the storage means,
Control that reads out a loop gain associated with the distance measured by the distance measuring unit from the storage unit, sets the loop gain as a threshold, and howling occurs when the loop gain estimated by the gain estimating unit approaches the threshold Means,
A sound device comprising: The acoustic device according to claim 1, comprising a plurality of speakers,
In accordance with an instruction from the control means, it further comprises display means for displaying various images,
The storage means further stores the distance between the speakers,
Based on the distance between the speakers, the distance measured by the distance measuring means, and the loop gain estimated by the gain estimating means, the control means determines the positional relationship between the speakers and microphones and the loop gain for each microphone position. An acoustic device for displaying on a display means. The storage means stores a distance from the speaker to the microphone and a default value of a loop gain in association with each other,
3. The control unit according to claim 1, wherein the control unit returns the loop gain that has been updated and registered to the default value when a predetermined time has elapsed after the loop gain estimated by the gain estimation unit has been updated and registered in the storage unit. Sound equipment.

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