JPH08223274A - Hand-free talking device - Google Patents

Abstract

PURPOSE: To effectively suppress howling and to realize a hand-free talking device with high sound quality inexpensively. CONSTITUTION: The device is made up of a speaker 30, plural microphones 31a, 31b arranged in the same case 3 with a different distance from the speaker 30, transmission signal amplifier means 21a, 21b provided corresponding to the microphones 31a, 31b and amplifying an output signal from the microphones 31a, 31b respectively, a direct coupling suppression processing section 50 suppressing a direct coupling component of a reception signal included in a transmission signal based on the output signal from the transmission signal amplifier means 21a, 21b, and an acoustic coupling suppression processing section 1 suppressing the acoustic coupling component of the reception signal included in the transmission signal with an adaptive filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device used for intercoms, telephones and the like, and more particularly to a hands-free voice communication device having a function of preventing howling.

[0002]

2. Description of the Related Art In a communication device equipped with a speaker and a microphone, when the call volume is raised, a part of the audio signal emitted from the speaker is fed back to the microphone, causing an oscillation phenomenon called howling. In particular,
The hands-free communication device has a problem that howling is likely to occur because the distance between the reception speaker and the transmission microphone is shorter than the distance to the caller.

FIG. 15 shows the configuration of a conventional hands-free communication device which suppresses the occurrence of such howling. This hands-free communication device includes a speaker 30 and one microphone 31 mounted in the same housing 3, an amplification means 20 for amplifying a received signal and outputting it to the speaker 30.
It is composed of an amplifying means 21 for amplifying a transmission signal output from the microphone 31 and an acoustic coupling suppression processing section 1.

The acoustic coupling suppression processing unit 1 includes A / D converters 12 and 13 for converting an input signal into a digital signal and D / A converters 14 and 15 for converting an output signal into an analog signal.
, Adaptive filter 10 and subtraction processing means 11. The adaptive filter 10 identifies a transfer function of an acoustic propagation system, and performs a convolution operation on the received signal converted into a digital signal and the identified transfer function to obtain an acoustic coupling component in the transmitted signal.

Here, the transfer function of the acoustic propagation system means that the received signal is the D / A converter 15, the amplification means 20, and the speaker 3.
0, the microphone 31, the amplifying means 21, and the A / D converter 12, and is a transfer function of a system that is transferred. The transfer function does not reflect the sound emitted from the speaker and is directly reflected by the microphone. There are a direct coupling component when propagated to the speaker and an indirect coupling component when sound emitted from the speaker is reflected by a reflector and indirectly propagates to the microphone.

The subtraction processing means 11 suppresses the acoustic coupling component from the transmission signal by obtaining the difference between the transmission signal converted into a digital signal and the output signal of the adaptive filter 10. By using this communication device, it is possible to prevent feedback from the reception signal to the transmission signal and suppress howling.

[0007]

However, in the conventional communication device, the sound propagation system from the speaker to the microphone suddenly changes due to the presence or absence of a reflector that reflects the sound emitted from the speaker and the temporal change of the reflection condition. When it changes to, it is necessary to update all the coefficients of the adaptive filter at high speed, so the operation tends to become unstable,
In addition, there is a problem that processing cannot be performed unless an expensive filter and its peripheral circuit are used.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hands-free communication device capable of effectively suppressing howling with relatively inexpensive hardware.

[0009]

A hands-free communication device according to the present invention according to claim 1 is a speaker for converting a received signal into a voice and outputting the voice, and a speaker for changing a distance from the speaker. Placed in the same cabinet,
A plurality of microphones for converting the transmitted voice into an electric signal and outputting the electric signal, and a transmission signal amplification means provided corresponding to each of the above microphones for amplifying an output signal from each microphone, and the above transmission signal amplification. A direct coupling suppression processing unit that suppresses the direct coupling component of the reception signal included in the transmission signal based on the output signal of the means, and an acoustic coupling that suppresses the acoustic coupling component of the reception signal included in the transmission signal by the adaptive filter. And a suppression processing unit.

According to a second aspect of the present invention, there is provided a hands-free communication device according to the first aspect, wherein the microphone of the hands-free communication device according to the first aspect is arranged in a position close to two microphones, that is, the speakers. It is composed of one microphone and a second microphone arranged far from the speaker, and the transmission signal amplifying means amplifies the output signals of the two transmission signal amplifying means, that is, the first microphone. The first speech signal amplifying means and the second speech signal amplifying means for amplifying the output signal of the second microphone, and the direct coupling suppression processing unit outputs the output of the first speech signal amplifying means. The signal delay means for delaying the signal, the amplification factor adjusting means for adjusting the amplification factor of the second transmission signal amplifying means, and the arithmetic processing means for obtaining the difference between these signals are provided. Constructed.

According to a third aspect of the present invention, there is provided a hands-free communication device according to the first aspect, wherein the microphone of the hands-free communication device according to the first aspect is arranged in a position close to two microphones, that is, the speakers. It is composed of one microphone and a second microphone arranged far from the speaker, and the transmission signal amplifying means amplifies the output signals of the two transmission signal amplifying means, that is, the first microphone. The first speech signal amplifying means and the second speech signal amplifying means for amplifying the output signal of the second microphone, and the direct coupling suppression processing unit outputs the output of the first speech signal amplifying means. A filter for convoluting a transfer function representing a ratio of a signal and a transfer function of an acoustic direct propagation system from a pre-identified speaker directly to each microphone; It constituted by an arithmetic processing means for calculating a difference between the output signal of the output signal and the second transmit signal amplifying means of the filter.

According to the fourth aspect of the present invention, the hands-free communication device according to the present invention corrects the distortion generated in the transmission signal in the output of the direct coupling processing unit of the hands-free communication device according to the first to third aspects. It is configured by providing distortion correction means.
In the hands-free communication device according to the present invention described in claim 5, the microphone of the hands-free communication device according to claim 1 is composed of three or more microphones,
The direct coupling suppression processing section is composed of an arithmetic processing means for obtaining the sum of the output signals of the transmission signal amplifying means.

According to a sixth aspect of the present invention, there is provided a hands-free communication device according to the first aspect, wherein the direct coupling suppression processing section of the hands-free communication device according to any one of the first to fifth aspects transmits the output transmission signal. Predetermined as a band to be
It is configured by providing a filter that selectively passes only predetermined frequency components. The hands-free communication device according to the present invention described in claim 7 is a band to be transmitted of the output transmission signal to the output of each transmission signal amplification means of the hands-free communication device according to claims 1 to 5. Each of the filters is configured to selectively pass only a predetermined frequency component.

[0014]

In the hands-free communication device according to the present invention as set forth in claim 1, a plurality of microphones arranged at different distances from the speaker transmit the transmitted voice including the voice by acoustic coupling from the speaker to each microphone. It is converted into an electric signal, and this electric signal is amplified by the transmission signal amplifying means provided corresponding to each microphone. In the direct coupling suppression processing unit, after the direct coupling component of the acoustic coupling component included in the transmission signal is suppressed based on these amplified transmission signals, the acoustic coupling suppression processing unit further transmits by the applied filter. The acoustic coupling component included in the speech signal is suppressed.

According to the second aspect of the present invention, in the direct coupling suppression processing unit of the hands-free speech communication apparatus according to the present invention, the direct coupling component of the transmission signal is made in phase by the delay means, and the transmission signal of the transmission signal is adjusted by the amplification factor adjusting means. After the direct coupling component has the same amplitude, a difference is obtained by the calculating means to suppress the direct coupling component included in the transmission signal. According to the third aspect of the present invention, the direct coupling suppression processing unit of the hands-free speech communication apparatus according to the present invention uses one transfer signal of the transfer function of the sound direct propagation system from one speaker to a microphone directly identified by the speaker. After performing a convolution operation on the transfer function representing the ratio, the difference between the output signal of the filter and the other transmission signal is obtained by the arithmetic processing means, and the direct coupling component included in the transmission signal is suppressed.

According to the fourth aspect of the present invention, the hands-free communication device corrects the distortion generated in the speech signal component of the transmission signal output by the direct coupling suppression processing section. In the hands-free communication device according to the present invention as set forth in claim 5, three or more microphones convert the transmission voice including the voice by the acoustic coupling from the speaker to the microphone into an electric signal, and the electric signal is transmitted to each microphone. It is amplified by the transmission signal amplifying means provided correspondingly. After the arithmetic processing means obtains the sum of these amplified transmission signals, the acoustic coupling suppression processing unit further suppresses the acoustic coupling component contained in the signal obtained by the summation by the adaptive filter.

According to the sixth aspect of the present invention, the hands-free communication device according to the present invention selects only a predetermined frequency component of the transmission signal output from the direct coupling suppression processing section by the filter and inputs it to the acoustic coupling suppression processing section. In the hands-free communication device according to the present invention as set forth in claim 7, only the predetermined frequency component of the transmission signal output by each transmission signal amplification means is filtered by the filter provided corresponding to each transmission signal amplification means. Select and input directly to the coupling suppression processing unit.

Here, the acoustic coupling component includes both the direct coupling component and the indirect coupling component included in the transmission signal, and the suppression of the direct coupling component or the acoustic coupling component means the direct coupling component or the acoustic coupling component. Not only when it is completely removed, but also when the direct coupling component or the acoustic coupling component is attenuated.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the structure of a hands-free communication device according to the present invention described in claims 1 and 2. This hands-free communication device has a speaker 3 attached to a housing 3.
0, the first microphone 31a and the second microphone 31b, the amplification unit 20 that amplifies the received signal and outputs it to the speaker 30, and the first transmission that amplifies the transmitted signal output by the microphones 31a and 31b. The signal amplification means 21a and the first transmission signal amplification means 21b, the direct coupling suppression processing section 50, and the acoustic coupling suppression processing section 1 are included.

The acoustic coupling suppression processing section 1 has an A / D converter 13 for converting an input signal into a digital signal and a D / A converter for converting an output signal into an analog signal, as in the conventional speech communication apparatus. 14 and 15, an adaptive filter 10, and a subtraction processing means 11, and the adaptive filter 1
0 indicates the transfer function of the acoustic propagation system, and the transmission is performed by convoluting the transmission signal converted into a digital signal, the reception signal converted into a digital signal, and the identified transfer function. Find the acoustic coupling component in the signal.

The microphones 31a and 31b are arranged so that the distances from the center of the speaker 30 are different, and the respective output signals are amplified by the transmission signal amplifying means 21a and 21b and input to the direct coupling suppression processing section 50. To be done. The direct coupling suppression processing unit 50 delays the output signal of the first transmission signal amplification unit 21a by the signal delay unit 50.
0, an amplification factor adjustment unit 501 that adjusts the amplification factor of the output signal of the second transmission signal amplification unit 21b, and a signal delay unit 5
00 and an arithmetic processing means 502 for obtaining the difference between the output signals of the amplification factor adjusting means 501.

The signal delay means 500 delays the transmission signal output from the first microphone 31a, so that the phase of the direct coupling component included in this transmission signal is transmitted by the second microphone 31b. Match the phase of the direct coupling component contained in the signal. Further, the amplification factor adjusting means 501 adjusts the amplification factor of the transmission signal output from the second microphone 31b, so that the first microphone 31a outputs the amplitude of the direct coupling component included in the transmission signal. To match the amplitude of the direct coupling component included in the transmitted signal.

Then, the arithmetic processing means 502 removes the direct coupling component contained in the transmission signal by obtaining the difference between these transmission signals. FIG. 2 shows an example of the appearance of the casing 3 of the hands-free communication device. A speaker 30 and microphones 31a and 31b are attached to the casing 3, and the distances from the center of the speaker 30 to the microphones 31a and 31b are L1 and L2, respectively.
Is.

The sound wave emitted from the speaker 30 is
Since the amplitude is attenuated in proportion to the distance from the speaker 30 and the phase is delayed in proportion to the distance from the speaker 30, the direct coupling component included in the transmission signal output from each microphone has a phase and an amplitude in the speaker. It will vary in proportion to the distance from 30. On the other hand, compared to the distance from the speaker 30 to the microphones 31a and 31b, the distance from the caller or the reflector to the microphones 31a and 31b is sufficiently long, so that the voices of the callers included in the transmission signal output from each microphone are emitted. Are equal in phase and amplitude.

Therefore, the two microphones 31a,
If the characteristics of 31b and the transmission signal amplifying means 21a and 21b are equal, the delay time τ of the signal delay means 500 and the amplification rate α of the amplification rate adjusting means 501 are τ = (L2-L1) / c (1) α = L2 / L1 (2) However, c represents the speed of sound. By such processing, the direct coupling suppression processing unit 50 can suppress the direct coupling component, and thus the acoustic coupling processing unit 1 mainly suppresses the indirect coupling component.

Here, the adaptive filter 10 updates its coefficient so as to minimize the acoustic coupling component contained in the transmission signal. For example, when the LMS algorithm based on the least square method is adopted as the algorithm, the filter coefficient is expressed as W (k + 1) = W (k) + 2μeX (k) (3). Here, W (k) is the coefficient vector of the filter at the sample time k, and X (k) is the sample time k.
The input vector of the filter in, μ is the step size determined as a number from 0 to 1, and e is the error signal.

Therefore, when the adaptive filter 10 is used to identify only the indirect coupling component, the order is reduced as compared with the conventional case where it is used to identify the entire acoustic coupling component including the direct coupling component. be able to. As a result, the calculation processing speed required for hardware can be relaxed, and howling can be effectively suppressed by relatively inexpensive hardware.

Here, in the case of an ordinary hands-free speech communication apparatus, the ratio of the direct coupling component and the indirect coupling component contained in the transmission signal is about 10: 1, and the direct coupling component is dominant. Therefore, if the direct coupling component can be sufficiently suppressed by the direct coupling suppression unit, howling can be effectively suppressed, and the howling can be performed even when the indirect coupling component varies due to changes in the surrounding environment. It is possible to prevent the occurrence of a call and make a stable call.

FIG. 3 shows an example of the configuration of the hands-free communication device according to the third aspect of the present invention. In this hands-free communication device, the direct coupling processing unit 51 is composed of A / D converters 510 and 511 that convert a transmission signal into a digital signal, a filter 512, and an arithmetic processing unit 513. The filter 512 performs a convolution operation of the output signal of the first transmission signal amplifying means 21a after digital conversion and a predetermined transfer function, and the operation processing means 513 causes the filter 5 to perform the convolution operation.
The direct coupling component contained in the transmission signal is suppressed by obtaining the difference between the output signal of 12 and the output signal of the second transmission signal amplifying means 21b after digital conversion.

The filter 512 has a coefficient of a direct coupling component based on a transfer function which represents a ratio of transfer functions of an acoustic direct propagation system from the speaker 30 which is identified in advance to the microphones 31a and 31b directly. Although the suppression amount is determined to be the maximum, unlike the indirect coupling component, the direct coupling component is not affected by the presence or absence of a reflector or the temporal change of the reflection condition, so this coefficient is a fixed value. be able to.

Therefore, for the direct coupling component that does not change in the acoustic propagation system, the filter 5 of the direct coupling suppression processing unit 51.
Since it can be suppressed by 13, the adaptive filter 10 of the acoustic coupling suppression processing unit 1 mainly suppresses the indirect coupling component that changes in the acoustic propagation system due to the surrounding environment and the like. The direct coupling suppression processing unit 51 and the acoustic coupling suppression processing unit 1
Can be realized by a DSP because both are digital processing.

An example of the structure for identifying the coefficient of the filter 512 is shown in FIGS. The identification method shown in FIG. 4 is a factory-ready type that is identified in advance in a factory, and the identification method shown in FIG. 5 is a site-ready type that is identified after the communication device is installed at a predetermined position. is there. In the case of a factory-compatible type, the white noise oscillator 6 is connected as a signal source to the reception signal amplifying means 20 without connecting the telephone terminal to the line system, and the output signal e of the arithmetic processing means 513 is an adaptive filter Connected to 512. Also,
In order to prevent the microphones 31a and 31b from picking up the indirect coupling component, the filter 512 is set using an algorithm that minimizes the signal e after the state where there is no reflection object in the surroundings.
The coefficient of is identified.

In the case of the field type, switching means S1 and S for switching between the call mode and the coefficient identification mode.
2 is provided and configured. In the call mode, the switching means S1 is connected to the side a and the switching means S1
1 is turned off, and has a configuration similar to that shown in FIG. On the other hand, in the coefficient identification mode, the switching means S1 is connected to the b side, the white noise oscillator 6 is connected to the D / A converter 15, the switching means S1 is turned on, and the signal e is configured as an adaptive filter. It is connected to the filter 512. The coefficient identification method of the filter 512 in the coefficient identification mode is the same as that in the factory type.

When the direct coupling suppression processing section 51 and the acoustic coupling suppression processing section 1 are realized by a DSP, the switching means S1, S2 can be realized as a soft switch by the instruction of the DSP control program. it can. FIG. 6 shows a configuration example of the hands-free communication device according to the fourth aspect of the present invention. In this hands-free communication device, the output of the direct coupling suppression processing unit 51 is provided with a distortion correction filter 8 for correcting a speech voice included in a transmission signal, that is, a component of a voice of a caller. The output signal of the distortion correction filter 8 is input to the acoustic coupling suppression unit 1.

As described above, the sound pressures generated at the positions of the two microphones 31a and 31b have the same phase and the same amplitude. This sound pressure is Ps, the characteristics of the two microphones 31a and 31b and the two signal amplifier means 21a and 21b are equal, and the transfer function of the microphone, the transmission signal amplifying means and the entire A / D converter is H. , And the transfer function of the filter is Wd, the utterance voice component included in the output signal of the direct coupling suppression processing unit 51 is H (1−Wd) Ps.

In the frequency characteristic of the transfer function H, the amplitude is substantially constant and the phase is a linear delay characteristic in the speech band, so that H can be regarded as a simple delay element. However, the frequency characteristic of the transfer function Wd depends on the shape and size of the speaker, the shape and size of the casing of the communication device, and
Since it is determined by the arrangement of the speaker and the microphone, it is generally complicated in the call band. That is, (1-Wd) is not just a delay characteristic.

Therefore, the direct coupling suppression processing section 51 causes distortion in the uttered voice component. The distortion correction filter 8 is a filter for correcting this distortion, and is configured as a digital filter in the present embodiment, but may be simply configured by an analog element. FIG. 7 shows a configuration example of the hands-free communication device according to the fifth aspect of the present invention. This hands-free communication device has a speaker 30 attached to the housing 3 and three or more microphones 31a to 31n, an amplifying unit 20 that amplifies a received signal and outputs it to the speaker 30, and outputs from the microphones 31a to 31n. The transmission signal amplification means 21a to 21n for amplifying the transmission signals respectively, the direct coupling suppression processing section 52 constituted by the arithmetic processing means 520,
It is configured by the acoustic coupling suppression processing unit 1.

Each of the above microphones 31a to 31n
Are arranged so that the distances from the center of the speaker 30 are different, and the respective output signals are transmitted signal amplifying means 21a.
˜21n, amplified by the arithmetic processing unit 520, and input to the acoustic coupling processing unit 1. The sound suppression processing unit 1 is configured in the same manner as in the above embodiment.

From the speaker 30 to each microphone 31a
Since the distance to ~ 31n is different, each microphone 3
The phase of the direct coupling component of the sound waves picked up by 1a to 31n differs depending on each microphone. On the other hand, the distance from the caller or the reflector to the microphones 31a to 31n is sufficiently longer than the distance from the speaker 30 to the microphones 31a to 31n.
The phases of the voice and the indirect coupling component emitted by the caller included in the transmission signals output by a to 31n are equal.

Therefore, each of the transmission signal amplifying means 21a-2a
When the output signals of 1n are added by the arithmetic processing means 520, only the direct coupling components are canceled and attenuated, while the voice component and the indirect coupling component of the caller are amplified. In this way, since the direct coupling component can be suppressed by the direct coupling suppression processing unit 52, the acoustic coupling processing unit 1 mainly suppresses the indirect coupling component.

The microphones 31a to 3a described above are used.
By arranging 1n in a row in the radial direction of the vibrating surface of the speaker 30, it is possible to give the sound collecting characteristic directivity. In particular, if the sound waves emitted from the speaker have directivity, by arranging the microphones in a line at an appropriate position to give directivity to the sound collection characteristics, it is possible to more effectively remove the direct coupling component. Becomes

FIG. 8 shows an example of the construction of the hands-free communication device according to the sixth aspect of the present invention. This hands-free speech communication device is configured such that a filter 7 is provided at the output of the direct coupling suppression processing unit 51 of the hands-free speech communication device shown in FIG. 3, and the output signal of the filter 7 becomes the input of the acoustic coupling suppression processing unit 1. To be done. The filter 7 is a digital filter that selectively passes only a predetermined frequency component, which is predetermined as a band to be transmitted, of the transmission signal output from the direct coupling suppression processing unit 51, and the predetermined filter. The pass band is determined in consideration of a human voice band, speaker characteristics, a call band, and the like.

Since the components other than the required frequency components are not input to the acoustic coupling suppression processing section 1 by the filter 7, the adaptive filter 10 does not need to identify the transfer function for the unnecessary frequency components. Therefore, the identification error can be reduced and the acoustic coupling component can be effectively suppressed. Also, ambient noise other than the voice signal picked up by the microphone is not transmitted to the line side, and the call quality can be improved.

FIG. 9 shows an example of the structure of the hands-free communication device according to the seventh aspect of the present invention. This hands-free communication device is provided with filters 7a and 7b at the outputs of the transmission signal amplifying means 21a and 21b of the hands-free communication device shown in FIG. 3, and the output signals of the filters 7a and 7b are directly coupled and suppressed. It is configured to be an input of the unit 51.

Like the filter 7, the filters 7a and 7b are filters that selectively pass only a predetermined frequency component of a transmission signal, which is predetermined as a band to be transmitted, and are analog filters. Composed.
Therefore, like the filter 7, the identification error of the adaptive filter 10 can be reduced, the acoustic coupling component can be effectively suppressed, and ambient noise other than the voice signal picked up by the microphone can be removed. , Can improve the call quality.

In addition, as a preprocessing of A / D conversion,
A low pass filter is required to prevent aliasing, but the output signals of the filters 7a and 7b are A /
If the sampling frequency fs of the D converters 510 and 511 is not included, that is, if the frequency components of fs / 2 or more are included,
The low-pass filter is unnecessary. This state is shown in FIG.
It shows in (a)-(e). 10A is an example of the frequency spectrum of the output signals of the microphones 31a and 31b, FIG. 10B shows the frequency characteristics of the low-pass filter, and FIG. 10D shows the frequency of the filters 7a and 7b. It is a figure which shows an example of a characteristic.

The output signal of the low-pass filter in this case is shown in FIG. 10 (c), and the output signals of the filters 7a and 7b are shown in FIG. 10 (e). As shown in the frequency spectrum of FIG. 10E, the output signals of the filters 7a and 7b are
If only the components of fs / 2 or less are provided, the filters 7a and 7b also have a function of preventing aliasing, and a low-pass filter becomes unnecessary.

Experiments for confirming the effects of the present invention and the results thereof will be described below. FIG. 11 shows the direct coupling suppression characteristics when the conventional method is used, and FIG. 12 shows the direct coupling suppression characteristics when the method according to the present invention is used. In addition, the configuration of the apparatus used for the measurement of FIG. 11 is shown in FIG.
FIG. 14 shows the configuration of the apparatus shown in FIG.

The conventional apparatus shown in FIG. 13 has the same configuration as the apparatus shown in FIG. 15, and the coefficient of the filter is adaptively updated so that the acoustic coupling component contained in the output signal of the subtracting means is minimized. It was On the other hand, the device according to the present invention shown in FIG. 14 has substantially the same configuration as the direct coupling suppression unit 51 of the hands-free speech communication device shown in FIG. 3, and as described above, the direct signal contained in the output signal of the subtraction means is included. The coefficients of the filter 512 are adaptively updated so that the combined component is minimized.

In this way, both of the adaptively updated devices are supplied to the A / D converter 13 as output signals of the white noise oscillator as reception signals in the acoustic-free room, and at that time, the D / A converter 1 is supplied.
The transmission signal output from No. 4 was observed by an FFT analyzer. 11 and 12 configure the above-described adaptive filter of each device as a filter having a tap number of 16 taps, 32 taps, and 64 taps, respectively, and adaptively update the coefficient to converge the coefficient and then output the output. The frequency characteristic of the direct coupling component included in the speech signal is shown. The sampling frequency was 8 kHz, and the cut-off frequency of the aliasing prevention low-pass filter was 3 kHz.

As can be understood from these measurement results,
It has been shown that the filter order required to obtain the same degree of direct coupling suppression effect is reduced to ¼ or less of the conventional method by the method according to the present invention.

[0052]

According to the first aspect of the present invention, in the hands-free speech communication apparatus according to the present invention, the direct coupling suppression processing section is provided in front of the acoustic coupling suppression processing section, and the direct coupling suppression processing section directly couples the acoustic coupling components. The adaptive filter is mainly used for suppressing the indirect coupling component because the component is suppressed.

Therefore, compared with the conventional case where the entire acoustic coupling component is processed by the adaptive filter, the required order of the adaptive digital filter can be reduced.
In addition, since the direct coupling component that occupies most of the acoustic coupling component can be sufficiently removed by the direct coupling suppression processing unit, even if the indirect coupling component fluctuates due to changes in the surrounding environment, it is stable. Howling suppression processing can be performed.

As a result, the calculation processing speed required for hardware can be relaxed, and howling can be effectively suppressed by relatively inexpensive hardware. That is, it is possible to inexpensively provide a hands-free communication device capable of suppressing howling stably and effectively. In the hands-free communication device according to the second aspect of the present invention, since the direct coupling suppression processing unit can be configured by a relatively simple analog circuit, a hands-free communication device that can suppress howling is provided at low cost. can do.

In the hands-free communication device according to the third aspect of the present invention, since the direct coupling suppression processing section is constituted by the digital filter, the shape and size of the vibration surface of the speaker and the acoustic-electric conversion characteristics of the two microphones. The difference between
In addition, since the suppression processing can be performed in consideration of the shape and size of the enclosure to which the speaker and the microphone are attached, the direct coupling component can be effectively suppressed, and howling can be effectively suppressed. It is possible to provide a hands-free communication device that can perform.

In the hands-free communication device according to the fourth aspect of the present invention, by providing the distortion correction means, it is possible to correct the distortion of the uttered voice caused by the direct coupling suppression process, and improve the communication quality. You can In the hands-free communication device according to the fifth aspect of the present invention, since the suppression processing can be performed by adding the output signals of three or more microphones having different distances from the speaker, howling is suppressed by a simple configuration. be able to. That is, it is possible to inexpensively provide a hands-free communication device capable of suppressing howling.

In the hands-free speech communication apparatus according to the sixth aspect of the present invention, the band to be identified by the adaptive filter can be limited by providing an analog filter that allows only a predetermined band to pass. Can be reduced, and the acoustic coupling component can be suppressed more effectively. Further, ambient noise other than the call band can be cut, and the call quality can be improved.

A hands-free communication device according to a seventh aspect of the present invention has the same effect as described above, and
Since it is provided in the preceding stage of the A / D converter, it can function as an anti-aliasing filter for preventing aliasing, and the low-pass filter normally used as an anti-aliasing filter can be reduced, which is more effective. It is possible to inexpensively provide a hands-free communication device that effectively suppresses acoustic coupling components and improves the communication quality.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a hands-free communication device according to the present invention described in claims 1 and 2.

FIG. 2 is a diagram showing an example of an external appearance of a casing of the hands-free communication device according to the present invention as set forth in claims 1 and 2.

FIG. 3 is a diagram showing a configuration example of a hands-free communication device according to the present invention as defined in claim 3;

FIG. 4 is a diagram showing a configuration example for identifying a coefficient of a filter of a direct coupling suppression processing section.

FIG. 5 is a diagram showing another configuration example for identifying the coefficient of the filter of the direct coupling suppression processing section.

FIG. 6 is a diagram showing a configuration example of a hands-free communication device according to the present invention as defined in claim 4;

FIG. 7 is a diagram showing a configuration example of a hands-free communication device according to the present invention as defined in claim 5;

FIG. 8 is a diagram showing a configuration example of a hands-free communication device according to the present invention according to claim 6;

FIG. 9 is a diagram showing a configuration example of a hands-free communication device according to the present invention as defined in claim 7;

FIG. 10 is a diagram showing an example of a frequency spectrum of a transmission signal and a frequency characteristic of a filter.

FIG. 11 is a diagram showing an observation result when a conventional method is used.

FIG. 12 is a diagram showing an observation result when the method according to the present invention is used.

13 is a diagram showing a configuration of an apparatus used for the observation of FIG.

14 is a diagram showing a configuration of an apparatus used for observation in FIG.

FIG. 15 is a diagram showing a configuration of a conventional communication device.

[Explanation of symbols]

 1 ... Acoustic coupling suppression processing unit 10 ... Adaptive filter 50, 51, 52 ... Direct coupling suppression processing unit 3 ... Case 30 ... Speakers 31a, 31b ... Microphone 20 ... Received signal amplifying means 21a, 21b ... Transmitting signal amplifying means 500 ... Signal delaying means 501 ... Amplification factor adjusting means 502, 513, 520 ... Arithmetic processing means 512, 7, 7a, 7b ...・ Filter 8 ・ ・ ・ Distortion correction means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kako Takura 1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works, Ltd.

Claims (7)

[Claims] 1. A speaker for converting a received signal into a voice and outputting the same and a microphone for converting a transmitted voice into an electric signal and outputting the same are installed in the same casing, and an acoustic coupling component from the speaker to the microphone is adaptively filtered. In the communication device including the acoustic coupling suppression processing unit that suppresses the microphone, the microphone is composed of a plurality of microphones arranged so that the distance from the speaker is different, and the microphone is provided corresponding to each of the microphones. Equipped with a transmitting signal amplifying means for amplifying each output signal from the microphone and a receiving signal amplifying means for amplifying an input signal to the speaker, which is included in the transmitting signal and directly circulates to the microphone through the speaker. A direct coupling suppression processing unit that suppresses a voice component based on the output signal of the transmission signal amplifying means. Is provided before the acoustic coupling suppression processing unit. 2. The microphone comprises a first microphone arranged in a position close to the speaker and a second microphone arranged in a position far from the speaker, and the transmission signal amplifying means comprises a first microphone. Of the first transmission signal amplifying means for amplifying the output signal of the microphone and the second transmission signal amplifying means for amplifying the output signal of the second microphone. Signal delay means for delaying the output signal of the transmission signal amplifying means, amplification factor adjusting means for adjusting the amplification factor of the second transmission signal amplifying means, and arithmetic processing means for obtaining the difference between these signals. The hands-free communication device according to claim 1, further comprising: 3. The microphone comprises a first microphone arranged in a position close to the speaker and a second microphone arranged in a position far from the speaker, and the transmission signal amplifying means comprises a first microphone. Of the first transmission signal amplifying means for amplifying the output signal of the microphone and the second transmission signal amplifying means for amplifying the output signal of the second microphone. A filter for performing a convolution calculation of the output signal of the transmission signal amplifying means and the transfer function representing the ratio of the transfer function of the acoustic direct propagation system from the speaker identified in advance to each microphone, and the output signal of the filter The hands-free communication device according to claim 1, further comprising: an arithmetic processing unit that obtains a difference from the output signal of the second transmission signal amplifying unit. 4. The hands-free call according to claim 1, wherein the output of the direct coupling processing unit is provided with distortion correction means for correcting the distortion of the uttered voice component generated in the transmission signal. apparatus. 5. The microphone is composed of three or more microphones, and the direct coupling suppression processing unit is composed of arithmetic processing means for obtaining a sum of output signals of the transmission signal amplifying means. The hands-free communication device according to claim 1. 6. A filter for selectively passing only a predetermined frequency component, which is predetermined as a band to be transmitted, of the output transmission signal is provided at the output of the direct coupling suppression processing unit. The hands-free communication device according to any one of claims 1 to 5. 7. A filter for selectively passing only a predetermined frequency component, which is predetermined as a band to be transmitted, of the output transmission signal is provided at the output of each transmission signal amplifying means. The hands-free communication device according to any one of claims 1 to 5, wherein