JP2007124162A - Loudspeaker call device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a loudspeaker call device capable of preventing the occurrence of howling, even if the received speech volume is increased. <P>SOLUTION: The loudspeaker call device comprises a microphone 1; a speaker 2; a 2-4 wire conversion circuit 3; a received signal amplifier VG; a voice switch 10; and first and second echo cancellers 30A, 30B. When a talker manually increases the amplification factor of the received signal amplifier VG to increase the received speech volume, the total loss amount calculation section 14 of the voice switch 10 increases the total loss by an amount nearly equal to the increment of the amplification factor of the received signal amplifier VG. As a result, since the increase in the loop gain of the closed loop formed by the acoustic side feedback path H<SB>AC</SB>and the line side feedback path H<SB>LIN</SB>is suppressed, even if the amplification factor of the received signal amplifier VG is increased, the occurrence of howling can be prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a loudspeaker communication apparatus such as an interphone that includes a microphone and a speaker and performs a loudspeaker call.

  In this type of loudspeaker, an uncomfortable echo (acoustic echo or acoustic echo) is caused by an acoustic return path formed by acoustic coupling of a microphone and a speaker, or a line-side return path formed between the other party's call terminal. Line echo) may be heard, or howling occurs at the frequency when a closed loop in which the loop gain in an arbitrary frequency component exceeds 1 is formed in the communication system by the feedback path or the like. In some cases, an echo canceller and a voice switch are provided in order to prevent the generation of unpleasant echoes and howling as described above (see, for example, Patent Document 1).

The voice switch includes a transmission side loss insertion unit that inserts loss into the signal path on the transmission side, a reception side loss insertion unit that inserts loss into the signal path on the reception side, and each loss insertion on the transmission side and reception side. And an insertion loss amount control unit for controlling a loss amount inserted from the unit. The insertion loss amount control unit is configured to return the acoustic side feedback (hereinafter referred to as “acoustic side feedback path”) that returns from the output point of the receiving side loss insertion unit to the input point of the transmission side loss insertion unit via the acoustic echo path. Line-side feedback gain of the path (hereinafter referred to as “line-side feedback path”) for estimating the gain and returning from the output point of the transmission-side loss insertion section to the input point of the reception-side loss insertion section via the line echo path And the total loss amount to be inserted into the closed loop based on the estimated values of the feedback gains on the acoustic side and the line side (the insertion loss amount of the transmission side loss insertion unit and the insertion loss amount of the reception side loss insertion unit) Sum)), and the call state is estimated by monitoring the transmission signal and the reception signal, and the transmission side loss insertion unit and the reception side loss insertion unit according to the estimation result and the calculated value of the total insertion loss amount The distribution of each insertion loss amount is determined. The echo canceller adaptively identifies the impulse response of the feedback path and estimates the pseudo echo component of the feedback path from the input signal to the feedback path, and the pseudo echo component estimated by the adaptive filter as the feedback path. And a subtracter that subtracts from the output signal from the.
JP 2002-359580 A

  By the way, in the above-mentioned loudspeaker device, when the function of manually increasing the volume of the received voice (hereinafter referred to as the received volume) sent from the speaker as a response to the elderly, the received volume is increased. As a result, the feedback gain on the acoustic side increases, so that the round-trip gain of the closed loop formed by the acoustic echo path and the line echo path also increases, and howling easily occurs.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a loudspeaker apparatus that can prevent howling even when the received sound volume is increased.

  In order to achieve the above object, the invention of claim 1 is a microphone that outputs the collected sound as a transmission signal, a speaker that rings in response to a reception signal from a call terminal on the other side, a microphone and a speaker. A first echo canceler that eliminates acoustic echo caused by acoustic coupling, and a second echo that eliminates line echo caused by signal coupling in the line between the acoustic coupling at the other party's call terminal and the other party's call terminal A voice switch that is provided between the canceller and the first and second echo cancellers, reduces a round-trip gain of a closed loop formed by the acoustic echo path and the line echo path, and suppresses howling; a voice switch; A reception signal that is provided between the echo cancellers, amplifies the reception signal output to the speaker, and has a variable amplification factor. The voice switch includes a transmission side loss insertion unit that inserts a loss into the signal path on the transmission side, a reception side loss insertion unit that inserts a loss into the signal path on the reception side, a transmission side, and Insertion loss amount control means for controlling the loss amount to be inserted from each loss insertion means on the receiver side, the insertion loss amount control means from the output point of the reception side loss insertion means via the acoustic echo path to the transmission side Estimate the acoustic feedback gain of the path returning to the input point of the loss insertion means, and return the line from the output point of the transmission loss insertion means to the input point of the reception loss insertion means via the line echo path A total loss amount calculation unit that estimates the side feedback gain and calculates the total amount of loss to be inserted into the closed loop based on the estimated values of the feedback gains on the acoustic side and the line side, and monitors the transmission signal and the reception signal To estimate the call state and And an insertion loss amount distribution processing unit that determines the distribution of each insertion loss amount of the transmission side loss insertion means and the reception side insertion loss means according to the calculated value of the total loss amount calculation unit, the total loss amount calculation unit is When the amplification level of the reception signal amplification means is increased, the total loss amount is increased by an amount substantially equal to the increase amount of the amplification level.

  According to a second aspect of the present invention, in the first aspect of the invention, the second echo canceller adaptively identifies an impulse response of a line echo path and estimates a pseudo echo component from an input signal to the line echo path. And a subtractor for subtracting the pseudo echo component estimated by the adaptive filter from the output signal from the line echo path, and the adaptive filter is a pseudo signal before the increase after the amplification degree of the received signal amplifying means is increased. The estimation result of the echo component is used.

  The invention of claim 3 is characterized in that, in the invention of claim 1 or 2, the received signal amplification means gently changes the amplification degree according to a predetermined time constant.

  According to the first aspect of the present invention, even when the amplification level of the reception signal amplification means is increased to increase the reception volume, the total loss amount calculation unit of the voice switch is an amount substantially equal to the increase of the amplification level. In order to increase the total loss amount, an increase in the closed loop loop gain formed by the acoustic echo path and the line echo path is suppressed, and it is possible to prevent the occurrence of howling.

  According to invention of Claim 2, there exists an effect similar to Claim 1.

  According to the third aspect of the present invention, there is an effect that howling can be more reliably prevented by reducing the load applied to the acoustic side feedback gain estimation process in the total loss amount calculation unit.

  As shown in FIG. 1, the present embodiment includes a microphone 1, a speaker 2, a 2-wire to 4-wire conversion circuit 3, a reception signal amplifier VG, a voice switch 10, and first and second echo cancellers 30A and 30B. .

The first echo canceller 30A includes a well-known structure composed of the adaptive filter 31A and a subtractor 32A, the impulse response of the feedback path (acoustic echo path) H _AC formed by the acoustic coupling between the speaker 2 microphone 1 The acoustic echo is suppressed by subtracting the pseudo echo component (acoustic echo) that is adaptively identified by the adaptive filter 31A and estimated from the reference signal (input signal to the speaker 2) from the output signal of the microphone 1 by the subtractor 32A. Is. The second echo canceller 30B also has a conventionally well-known configuration including an adaptive filter 31B and a subtractor 32B. The reflection due to impedance mismatch between the 2-wire-to-wire conversion circuit 3 and the transmission path and the counterpart The impulse response of the feedback path (line echo path) H _LIN formed by the acoustic coupling between the speaker and the microphone in the telephone terminal (for example, intercom system door phone slave unit) is adaptively identified by the adaptive filter 31B and referred to The line echo is suppressed by subtracting the pseudo echo component (line echo) estimated from the signal (input signal to the 2-wire to 4-wire conversion circuit 3, that is, transmission signal) from the reception signal by the subtractor 32B. .

The voice switch 10 includes a transmission side loss insertion unit 11 that inserts a loss into the signal path on the transmission side, a reception side loss insertion unit 12 that inserts a loss into the signal path on the reception side, and a transmission side and a reception side. And an insertion loss amount control unit 13 that controls the amount of loss inserted from each of the loss insertion units 11 and 12. The insertion loss amount control unit 13, the path to return to the input point Tin of the transmitting end losses insertion portion 11 from the output point Rout of the receiving-side loss insertion portion 12 via the acoustic echo path H _AC (hereinafter, "sound side feedback path )) And a return path from the output point Tout of the transmission side loss insertion unit 11 to the input point Rin of the reception side loss insertion unit 12 via the line echo path H _LIN (hereinafter referred to as “reception side feedback gain α”). (Referred to as “line-side feedback path”), and the loss amount to be inserted into the closed loop is estimated based on the estimated values α ′ and β ′ of the feedback gains α and β on the acoustic side and the line side. A total loss amount calculation unit 14 that calculates the sum (the sum of the insertion loss amount of the transmission side loss insertion unit 11 and the insertion loss amount of the reception side loss insertion unit 12), and the state of the call by monitoring the transmission signal and the reception signal According to the estimation result and the total loss calculation unit 14 It comprises an insertion loss amount distribution processing unit 15 that determines the distribution of each insertion loss amount of the side loss insertion unit 11 and the reception side loss insertion unit 12. The first and second echo cancellers 30A and 30B and the voice switch 10 according to the present embodiment control the DSP (Digital Signal Processor) hardware by software (programs) for the echo canceller and the voice switch. It has been realized. Therefore, the input / output signals (received signal and transmitted signal) of the voice switch 10 and the first and second echo cancellers 30A and 30B in the following description are sampled at a predetermined sampling period and quantized by the A / D converter. It has become.

The total loss amount calculation unit 14 estimates the time-average power of the input signal of the transmission side loss insertion unit 11 in a short time using a rectifier / smoothing device, a low-pass filter, and the like. estimating the time average power in a short time of the output signal of the receiving-side loss insertion portion 12 with a like, time of the output signal of the receiving-side loss insertion portion 12 in the maximum delay time assumed in acoustic side feedback path H _AC A minimum value of the estimated value of the average power is obtained, and a value obtained by dividing the estimated value of the time average power of the input signal of the transmission side loss insertion unit 11 by this minimum value is set as the estimated value α ′ of the acoustic feedback gain α. The time average power of the input signal of the receiving side loss insertion unit 12 in a short time is estimated using a rectifying / smoothing device, a low-pass filter, etc. Insertion part 11 Estimating the time average power in a short time of the signal, determining the minimum value of the estimated value of the time average power of the output signal of the transmitter-side loss insertion unit 11 at the maximum delay time assumed in the line side feedback path H _LIN, A value obtained by dividing the estimated value of the time average power of the input signal of the receiving side loss insertion unit 12 by this minimum value is defined as an estimated value β ′ of the line side feedback gain β. Then, the total loss calculation unit 14 calculates a total loss Lt necessary to obtain a desired gain margin MG from the estimated values α ′ and β ′ of the acoustic feedback gain α and the line feedback gain β. The value Lt is output to the insertion loss amount distribution processing unit 15.

  The insertion loss amount distribution processing unit 15 monitors the input / output signals of the transmission side loss insertion unit 11 and the input / output signals of the reception side loss insertion unit 12, and compares the power levels of these signals and the presence / absence of a voice signal. The communication state (the reception state, the transmission state, etc.) is determined from the information of the information, and the total loss Lt is distributed to the transmission side loss insertion unit 11 and the reception side loss insertion unit 12 at a rate corresponding to the determined communication state. The insertion loss amount of each loss insertion part 11 and 12 is adjusted so that it may.

  By the way, as described above, the total loss amount calculation unit 14 according to the present embodiment calculates and adaptively updates the sum of loss amounts to be inserted into the closed loop based on the estimated values α ′ and β ′ of the feedback gains α and β. There are two operation modes, an update mode and a fixed mode for fixing the total loss amount to a predetermined initial value, and the first and second echo cancellers 30A and 30B are sufficiently provided from the start of a call with the other party's call terminal. It operates in the fixed mode during the period until convergence, and operates in the update mode during the period after the first and second echo cancellers 30A and 30B have sufficiently converged. That is, in the total loss amount calculation unit 14, the estimated values α ′ and β ′ of the acoustic side feedback gain α and the line side feedback gain β are continuously maintained for a predetermined time (several hundred milliseconds) for a predetermined threshold value ε ( For example, it is considered that the first and second echo cancellers 30A and 30B have sufficiently converged when the values are less than 10 dB to 15 dB smaller than the estimated values α ′ and β ′ at the start of the call, Before, the operation mode is switched to the update mode in which the total loss amount is adaptively updated based on the estimated values α ′ and β ′. Note that the initial value of the total loss amount in the fixed mode is set to a value sufficiently larger than the total loss amount updated as needed in the update mode.

  Thus, when the first and second echo cancellers 30A and 30B immediately after the start of the call are not sufficiently converged, the total loss amount calculation unit 14 operating in the fixed mode sets the value sufficiently large. Since the initial total loss amount is inserted into the closed loop, it is possible to suppress the generation of unpleasant echoes (acoustic echoes and line echoes) and howling, and realize a stable half-duplex call. In the state where the first and second echo cancellers 30A and 30B have sufficiently converged after the time from the start of the call, the operation mode of the total loss calculation unit 14 is switched from the fixed mode to the update mode and closed loop. Since the total loss amount to be inserted into the value decreases to a value sufficiently lower than the initial value, two-way simultaneous calls can be realized.

  Here, the specific operation of the total loss amount calculation unit 14 in the update mode will be described with reference to the flowchart of FIG.

  The total loss amount calculation unit 14 executes an estimation process of the acoustic side feedback gain α and the line side feedback gain β at a predetermined sampling period from the time when the fixed mode is changed to the update mode (t = t1), and the estimated value α '(n), β' (n) is calculated (step 1), and the gain margin of the closed loop MG [is calculated from the product of these two estimated values α '(n), β' (n) and the gain margin MG. The desired total loss amount Lr (n) required for maintaining the value [dB] is calculated by the following equation (step 2).

Lr (n) = 20 log | α ′ (n) · β ′ (n) | + MG [dB]
Note that α ′ (n), β ′ (n), and Lr (n) indicate an estimated value of feedback gain and a desired total loss amount calculated by sampling n times from the update mode transition point, respectively. Further, the total loss amount calculation unit 14 calculates the n-th total loss amount desired value Lr (n) calculated from the above formula and the previous (n−1) th total loss amount Lt (n−1), that is, the previous process. When the desired total loss amount Lr (n) calculated this time is larger than the total loss amount determined and actually inserted, a slight increase Δi [dB in the previous total loss amount Lt (n−1). ] Is defined as the total loss amount Lt (n) = Lt (n−1) + Δi (steps 3 and 4), and the total loss calculated this time with respect to the previous total loss amount Lt (n−1). When the loss desired value Lr (n) is small, the current total loss Lt (n) = Lt (n) is obtained by subtracting a slight decrease Δd [dB] from the previous total loss Lt (n−1). −1) −Δd (steps 5 and 6).

  Thus, by suppressing the increase / decrease in the total loss amount by the total loss amount calculation unit 14 to a small value of Δi or Δd, the first and second echo cancellers 30A can be used just after the start of a call with the other party's call terminal. , 30B actively update the coefficient toward convergence, so that a sense of incongruity can be eliminated even when the acoustic feedback gain α and the line feedback gain β change significantly.

By the way, in this embodiment, the reception signal amplifier VG is provided in the signal path on the reception side between the voice switch 10 and the first echo canceller 30A. In this reception signal amplifier VG, the amplification level is manually increased or decreased by a speaker who is talking to the other party's call terminal using this embodiment. For example, the speaker is an elderly person whose hearing ability has decreased. However, by increasing the amplification level of the reception signal amplifier VG and increasing the reception volume, the reception voice can be easily heard. Here, when increasing the amplification degree of the receiving signal amplifier VG as described in the prior art, because thereby increasing acoustic side feedback gain α by receiver volume is increased, the acoustic side feedback path H _AC and the line side feedback The round loop gain formed by the path H _LIN also increases, and howling is likely to occur.

Therefore, in this embodiment, when the speaker manually increases the amplification level of the reception signal amplifier VG to increase the reception volume, the total loss amount calculation unit 14 of the voice switch 10 increases the amplification level of the reception signal amplifier VG. The total loss is increased by an amount approximately equal to the minute. As a result, even if the amplification factor of the reception signal amplifier VG is increased, an increase in the closed loop loop gain formed by the acoustic side feedback path H _{AC and the} line side feedback path H _LIN is suppressed, thereby preventing howling. be able to. Here, the amplification degree of the reception signal amplifier VG returns to the initial value every time a call is finished, and therefore the total loss calculation unit 14 is an amount substantially equal to the increase in the amplification degree of the reception signal amplifier VG. The total loss amount is increased only during the call in which the speaker manually increases the amplification level of the reception signal amplifier VG to increase the reception volume, and operates in the above-described fixed mode at the next call.

  Even when the speaker manually increases the amplification level of the reception signal amplifier VG to increase the reception volume, the total loss amount calculation unit 14 is substantially equal to the increase in the amplification level of the reception signal amplifier VG. Since the line-side feedback gain β is hardly affected by increasing the total loss amount only, the adaptive filter 31B of the second echo canceller 30B is a pseudo signal before the increase even after the amplification factor of the reception signal amplifier VG is increased. The estimation result of the echo component may be used as it is.

  Further, when the reception signal amplifier VG increases or decreases the amplification degree, it is desirable to change the amplification degree gently according to a predetermined time constant. That is, when the amplification degree (reception volume) of the reception signal amplifier VG changes abruptly, an excessive load is applied to the process of obtaining the estimated value α ′ of the acoustic feedback gain α in the total loss amount calculation unit 14 of the voice switch 10. However, it is possible to reduce the load on the process for obtaining the estimated value α ′ by gradually changing the amplification degree. Here, the adaptive filter 31A included in the first echo canceller 30A is composed of a digital FIR filter, and the filter coefficient is determined by an algorithm that operates to minimize the erasure error that has not been eliminated by subtraction of the pseudo echo component. Are being corrected sequentially. Therefore, for the adaptive filter 31A of the first echo canceller 30A, the time constant when the amplification degree is gradually changed may be set to a value such that the filter coefficient to be sequentially corrected does not diverge. An appropriate value may be determined by performing an experiment to confirm the divergence of the filter coefficient while changing the value.

It is a block diagram which shows embodiment of this invention. It is a flowchart for operation | movement description of a voice switch in the same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microphone 2 Speaker 10 Voice switch 11 Transmission side loss insertion part 12 Reception side loss insertion part 13 Insertion loss amount control part 14 Total loss amount calculation part 30A 1st echo canceller 30B 2nd echo canceller VG Received signal amplifier

Claims (3)

A microphone that outputs collected sound as a transmission signal, a speaker that rings in response to a reception signal from a call terminal on the other side, and a first echo canceller that eliminates acoustic echo generated by acoustic coupling between the microphone and the speaker; A second echo canceler for canceling line echo caused by acoustic coupling at the other party's call terminal and signal wraparound on the line with the other party's call terminal, and between the first and second echo cancellers A voice switch that suppresses howling by reducing a closed loop loop gain formed by the acoustic echo path and the line echo path, and a reception signal that is provided between the voice switch and the first echo canceller and is output to the speaker Receiving signal amplifying means with a variable amplification degree,
The voice switch includes transmission side loss insertion means for inserting loss into the signal path on the transmission side, reception side loss insertion means for inserting loss into the signal path on the reception side, and insertion of each loss on the transmission side and reception side Insertion loss amount control means for controlling the amount of loss inserted from the means, the insertion loss amount control means, the input point of the transmission side loss insertion means from the output point of the reception side loss insertion means via the acoustic echo path And estimate the line-side feedback gain of the path that returns from the output point of the transmission-side loss insertion means to the input point of the reception-side loss insertion means via the line echo path. A total loss amount calculation unit for calculating the sum of loss amounts to be inserted into the closed loop based on the estimated values of the feedback gains on the acoustic side and the line side, and the call state is estimated by monitoring the transmission signal and the reception signal. , This estimation result and the total loss calculation part Consists insertion loss amount distribution processing section for determining the distribution of the insertion loss of the transmitting end losses insertion means and the receiving side insertion loss means in accordance with output values,
The total loss amount calculation unit increases the total loss amount by an amount substantially equal to the increase in the amplification level when the amplification level of the received signal amplification means increases.   The second echo canceller adaptively identifies the impulse response of the line echo path and estimates the pseudo echo component from the input signal to the line echo path, and the line of the pseudo echo component estimated by the adaptive filter. The subtractor for subtracting from the output signal from the echo path, and the adaptive filter uses the estimation result of the pseudo echo component before the increase even after the amplification degree of the received signal amplification means is increased. The loudspeaker apparatus according to 1.   The loudspeaker apparatus according to claim 1 or 2, wherein the reception signal amplifying means gently changes the amplification degree according to a predetermined time constant.

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