Input/output device and speech terminal

The technology disclosed herein relates to an input / output device including a speaker and a microphone.

Conventionally, when double talk occurs in a telephone conference system or the like, the coefficient sequence of the adaptive filter circuit is updated in order to suppress the occurrence of echo and howling caused by the reception signal output from the speaker being picked up by the microphone. A method of stopping has been proposed (see, for example, Patent Document 1). According to the method of Patent Document 1, when the echo path is changed due to the mute of the speaker or the microphone, it is possible to avoid changing the learned coefficient sequence.

<p num="0003"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 5-48547</text></patcit></p>

<p num="0004"> However, in the method of Patent Document 1, even if the coefficient sequence update of the adaptive filter circuit is stopped, the pseudo-echo signal generated by the convolution integral operation of the received signal sequence and the coefficient sequence is subtracted from the transmitted signal and output. Remains. Therefore, echo or howling may occur when the pseudo-echo signal is transmitted to the other party. An object of the technique disclosed herein is to provide an input / output device capable of suppressing the occurrence of echo and howling.</p>

<p num="0005"> The input / output device disclosed herein includes a speaker, a microphone, an adaptive filter circuit, and a control circuit. The speaker outputs voice based on the received signal. The microphone generates a transmission signal by collecting voice. The adaptive filter circuit outputs the residual signal based on the pseudo-echo signal generated from the transmission coefficient and the received signal indicating the voice transmission characteristic between the speaker and the microphone, and the transmitted signal amplified by the microphone amplifier circuit. Generate. The control circuit stops the output of the residual signal from the adaptive filter when muting at least one of the speaker and the microphone.</p>

<p num="0006"> The input / output device disclosed herein includes a speaker, a microphone, an adaptive filter circuit, and a control circuit. The speaker outputs voice based on the received signal. The microphone generates a transmission signal by collecting voice. The adaptive filter circuit outputs the residual signal based on the pseudo-echo signal generated from the transmission coefficient and the received signal indicating the voice transmission characteristic between the speaker and the microphone, and the transmitted signal amplified by the microphone amplifier circuit. Generate. The control circuit<u style="single">, Ma</u>I<u style="single">Ku</u>Adaptive filter when muted<u style="single">circuit</u>Stops the output of the residual signal from.</p>

<figref num="1">Block diagram of the input / output device according to the first embodiment</figref><figref num="2">Block diagram of the input / output device according to the second embodiment</figref><figref num="3">Block diagram of the input / output device according to the third embodiment</figref><figref num="4">Block diagram of the input / output device according to the fourth embodiment</figref><figref num="5">Block diagram of the input / output device according to the fifth embodiment</figref>

1. First embodiment (Configuration of I / O device 1) FIG. 1 is a block diagram of the input / output device 1 according to the first embodiment. The input / output device 1 includes a speaker and a microphone, and is preferably used for a telephone terminal capable of bidirectionally exchanging audio signals with the other terminal. Although not shown, such a call terminal is a receiver that receives the received signal X (t) from the other terminal and a transmitter that transmits the transmitted signal Y (t) output from the input / output device 1 to the other terminal. And, it suffices to have.

The input / output device 1 controls the input terminal 100, the speaker amplifier circuit 101, the speaker 102, the microphone 103, the microphone amplifier circuit 104, the adaptive filter circuit 120, the output terminal 108, the mute signal input unit 114, and the like. It includes a circuit 115. The received signal X (t) is input to the input terminal 100. The received signal X (t) is output from the input terminal 100 to each of the speaker amplifier circuit 101 and the adaptive filter circuit 120.

The speaker amplifier circuit 101 amplifies the received signal X (t) output from the input terminal 100. The speaker amplifier circuit 101 outputs the amplified received signal X (t) to the speaker 102. However, the speaker amplifier circuit 101 stops the amplification and output of the received signal X (t) when the stop signal is input from the control circuit 115. As a result, the input of the received signal X (t) to the speaker 102 is stopped while the speaker 102 is muted.

The speaker 102 is connected to the speaker amplifier circuit 101. The speaker 102 outputs a voice based on the received signal X (t) amplified by the speaker amplifier circuit 101. The microphone 103 generates a transmission signal Y (t) based on the voice collected from the surroundings. The microphone 103 outputs the transmission signal Y (t) to the microphone amplifier circuit 104. The microphone amplifier circuit 104 amplifies the transmission signal Y (t) input from the microphone 103. The microphone amplifier circuit 104 outputs the amplified transmission signal Y (t) to the adaptive filter circuit 120. However, when the stop signal is input from the control circuit 115, the microphone amplifier circuit 104 stops the generation and output of the transmission signal Y (t). As a result, the input of the transmission signal Y (t) to the adaptive filter circuit 120 is stopped while the microphone 103 is muted.

The received signal X (t) output from the input terminal 100 and the transmitted signal Y (t) output from the microphone amplifier circuit 104 are input to the adaptive filter circuit 120. The adaptive filter circuit 120 has a function of removing the audio component output from the speaker 102 and collected by the microphone 103 from the transmission signal Y (t). As a result, the occurrence of echo and howling in the transmission signal Y (t) is suppressed.

The adaptive filter circuit 120 includes the received signal input terminal 109, the received signal storage circuit 110, the coefficient storage circuit 113, the product-sum calculation circuit 112, the transmitted signal input terminal 105, the subtraction circuit 106, and the coefficient correction circuit 111. And a transmission signal output terminal 107. The received signal X (t) output from the input terminal 100 is input to the received signal input terminal 109. The received signal input terminal 109 outputs the received signal X (t) to the received signal storage circuit 110 and the coefficient correction circuit 111.

The received signal storage circuit 110 stores the received signal X (t) input from the received signal input terminal 109. The coefficient storage circuit 113 stores a transmission coefficient indicating a voice transmission characteristic in the space between the speaker 102 and the microphone 103. The transfer coefficient stored in the coefficient storage circuit 113 is updated by the coefficient correction circuit 111.

The product-sum calculation circuit 112 performs a convolution integral calculation of the received signal X (t) stored in the received signal storage circuit 110 and the transfer coefficient stored in the coefficient storage circuit 113, thereby performing a pseudo-echo signal Z (t). To generate. The product-sum calculation circuit 112 outputs the generated pseudo-echo signal Z (t) to the subtraction circuit 106. However, the product-sum calculation circuit 112 stops the generation of the pseudo-echo signal Z (t) according to the control signal output from the control circuit 115. As a result, when the speaker 102 and / and the microphone 103 are muted, the input of the pseudo echo signal Z (t) to the subtraction circuit 106 is stopped.

The transmission signal Y (t) output from the microphone amplifier circuit 104 is input to the transmission signal input terminal 105. The transmission signal input terminal 105 outputs the transmission signal Y (t) to the subtraction circuit 106. The subtraction circuit 106 generates a residual signal E (t) by subtracting the pseudo-echo signal Z (t) from the transmission signal Y (t). As a result, the audio component output from the speaker 102 and collected by the microphone 103 is removed from the transmission signal Y (t). The subtraction circuit 106 outputs the residual signal E (t) to the coefficient correction circuit 111 and the transmission signal output terminal 107, respectively.

However, as described above, when the microphone 103 is muted, the input of the transmission signal Y (t) from the microphone amplifier circuit 104 to the adaptive filter circuit 120 is stopped. Further, while the microphone 103 is muted, the input of the pseudo-echo signal Z (t) from the product-sum calculation circuit 112 to the subtraction circuit 106 is stopped. Therefore, while the microphone 103 is muted, the transmission signal Y (t) and the pseudo-echo signal Z (t) are not input to the subtraction circuit 106, so that no signal is output from the subtraction circuit 106.

Further, as described above, when the speaker 102 is muted, the input of the pseudo-echo signal Z (t) from the product-sum calculation circuit 112 to the subtraction circuit 106 is stopped. On the other hand, if the microphone 103 is not muted, the transmission signal Y (t) is input to the subtraction circuit 106. Therefore, while only the speaker 102 is muted, the subtraction circuit 106 outputs the transmission signal Y (t) as it is as the residual signal E (t).

In this way, when either the speaker 102 or the microphone 103 is muted, the residual signal E (t) generated based on the pseudo echo signal Z (t) and the transmission signal Y (t). The output from the adaptive filter circuit 120 of is stopped. The coefficient correction circuit 111 calculates the update value of the transmission coefficient between the speaker 102 and the microphone 103 based on the residual signal E (t) so that the output of the subtraction circuit 106 is minimized. The coefficient correction circuit 111 stores the updated value of the transmission coefficient in the coefficient storage circuit 113. As a result, even when the transmission coefficient between the speaker 102 and the microphone 103 fluctuates, the occurrence of echo and howling in the transmission signal Y (t) is suppressed. However, the coefficient correction circuit 111 stops the calculation of the update value of the transmission coefficient according to the control signal output from the control circuit 115. In this case, the coefficient correction circuit 111 does not store the updated value of the transfer coefficient in the coefficient storage circuit 113.

The transmission signal output terminal 107 outputs the residual signal E (t) and the transmission signal Y (t) generated from the transmission signal Y (t) by the adaptive filter circuit 120. The residual signal E (t) and the transmission signal Y (t) output from the adaptive filter circuit 120 are input to the output terminal 108. The output terminal 108 outputs the residual signal E (t) and the transmission signal Y (t) to an external device or the like.

A speaker mute signal indicating a mute operation of the speaker 102 is input to the mute signal input unit 114. The speaker mute signal is generated by pressing the speaker mute button on the remote controller (not shown) when the user wants to temporarily stop the output of the sound from the speaker 102. Further, a microphone mute signal indicating a mute operation of the microphone 103 is input to the mute signal input unit 114. The microphone mute signal is generated by pressing the microphone mute button on the remote controller when the user wants to temporarily stop the sound collection by the microphone 103.

A speaker mute signal and / or a microphone mute signal is input to the control circuit 115 from the mute signal input unit 114. The control circuit 115 outputs a stop signal for stopping the speaker amplifier circuit 101 to the speaker amplifier circuit 101 in response to the speaker mute signal. This mutes the speaker 102. The control circuit 115 outputs a stop signal for stopping the microphone amplifier circuit 104 to the microphone amplifier circuit 104 in response to the microphone mute signal. This mutes the microphone 103. Further, the control circuit 115 outputs a control signal for stopping the update value calculation of the coefficient series in the coefficient correction circuit 111 to the coefficient correction circuit 111 during the mute period of the speaker 102 and / and the microphone 103. Further, the control circuit 115 outputs a control signal for stopping the convolution integral calculation in the product-sum calculation circuit 112 to the product-sum calculation circuit 112 during the mute period of the speaker 102 and / and the microphone 103.

(Action and effect) (1) In the input / output device 1 according to the first embodiment, the adaptive filter circuit 120 has a pseudo echo signal Z (t) and a transmission signal Y (when either the speaker 102 or the microphone 103 is muted. The output of the residual signal E (t) generated based on t) and is stopped. Specifically, when the speaker amplifier circuit 101 and / and the microphone amplifier circuit 104 are stopped, the control circuit 115 also stops the convolution integral calculation in the product-sum calculation circuit 112.

Therefore, when the echo path is cut off by stopping the speaker amplifier circuit 101 and / and the microphone amplifier circuit 104, the path formed by the product-sum calculation circuit 112 and the subtraction circuit 106 is cut off. Therefore, the pseudo-echo signal Z (t) is subtracted from the transmission signal Y (t) even though the speaker 102 is muted, or the code is inverted even though the microphone 103 is muted. It is possible to suppress the generation of the signal Z (t). As a result, the occurrence of echo and howling can be suppressed.

(2) Further, in the input / output device 1 according to the first embodiment, when the speaker amplifier circuit 101 and / and the microphone amplifier circuit 104 are stopped, the control circuit 115 also updates the coefficient sequence in the coefficient correction circuit 111. Stop it. Therefore, for example, when only the speaker 102 is muted and the audio component output from the speaker 102 is not included in the transmission signal Y (t), the transmission coefficient is based on the transmission signal Y (t). Can be suppressed from being updated. Therefore, when the mute of the speaker 102 is released, an appropriate pseudo-echo signal Z (t) based on the learned transmission coefficient can be generated. As a result, echo and howling can be suppressed quickly after the mute is released.

2. Second embodiment (Configuration of I / O device 1) FIG. 2 is a block diagram of the input / output device 1 according to the second embodiment. The difference from the first embodiment of the second embodiment is that the control circuit 115 stops the processing in the subtraction circuit 106 instead of stopping the convolution integral calculation in the product-sum calculation circuit 112. In the following, the differences will be mainly described.

When the speaker mute signal and / and the microphone mute signal are input from the mute signal input unit 114, the control circuit 115 stops the process of subtracting the pseudo echo signal Z (t) from the transmission signal Y (t) in the subtraction circuit 106. Let me. As a result, when the transmission signal Y (t) is input from the transmission signal input terminal 105, the subtraction circuit 106 passes the transmission signal Y (t) as a residual signal E (t) as it is, and transmits the transmission signal Y (t). If the transmission signal Y (t) is not input from the signal input terminal 105, no signal is output.

(Action and effect) (1) In the input / output device 1 according to the second embodiment, the adaptive filter circuit 120 has a pseudo echo signal Z (t) and a transmission signal Y (when either the speaker 102 or the microphone 103 is muted. The output of the residual signal E (t) generated based on t) and is stopped. Specifically, when the speaker amplifier circuit 101 and / and the microphone amplifier circuit 104 are stopped, the control circuit 115 stops the process of subtracting the pseudo echo signal Z (t) from the transmission signal Y (t) in the subtraction circuit 106. Let me. Therefore, as in the first embodiment, the pseudo echo signal Z (t) is subtracted from the transmission signal Y (t) even though the speaker 102 is muted, or the microphone 103 is muted. Regardless, it is possible to suppress the generation of the pseudo-echo signal Z (t) whose code is inverted. As a result, the occurrence of echo and howling can be suppressed.

(2) Further, as in the first embodiment, the control circuit 115 stops the update of the coefficient sequence in the coefficient correction circuit 111, so that echo and howling can be quickly suppressed after the mute is released. ..

3. Third embodiment (Configuration of I / O device 1) FIG. 3 is a block diagram of the input / output device 1 according to the third embodiment. The difference from the first embodiment of the third embodiment is that the adaptive filter circuit 120 includes an output cutoff circuit 117 after the subtraction circuit 106. In the following, the differences will be mainly described. In this embodiment, it is assumed that the microphone 103 is muted.

The output cutoff circuit 117 is arranged between the subtraction circuit 106, the transmission signal output terminal 107, and the coefficient correction circuit 111. When the stop signal is input from the control circuit 115, the output cutoff circuit 117 stops the output of the signal input from the subtraction circuit 106. As a result, while the microphone 103 is muted, the output of the residual signal E (t) to the transmission signal output terminal 107 and the coefficient correction circuit 111 is stopped.

When the microphone mute signal is input from the mute signal input unit 114, the control circuit 115 outputs a control signal for stopping the output from the output cutoff circuit 117 to the output cutoff circuit 117. As a result, the signal output from the subtraction circuit 106 is cut off by the output cutoff circuit 117. In the present embodiment, since the control circuit 115 does not stop the processing of the microphone amplifier circuit 104, the product-sum calculation circuit 112, and the subtraction circuit 106, the residual signal E (t) from the subtraction circuit 106 to the output cutoff circuit 117. Is output.

Further, in the present embodiment, the control circuit 115 does not stop the processing of the coefficient correction circuit 111, but the output from the output cutoff circuit 117 is stopped at all, so that the coefficient correction circuit 111 has an updated value of the transmission coefficient. Is not calculated. As a result, the transfer coefficient stored in the coefficient storage circuit 113 is retained while the microphone 103 is muted.

(Action and effect) In the input / output device 1 according to the third embodiment, the adaptive filter circuit 120 is a residual generated based on the pseudo echo signal Z (t) and the transmission signal Y (t) when the microphone 103 is muted. Stop the output of signal E (t). Specifically, when the microphone mute signal is input from the mute signal input unit 114, the control circuit 115 cuts off the signal output from the subtraction circuit 106 by the output cutoff circuit 117.

Therefore, as in the first embodiment, it is possible to suppress the output of the residual signal E (t) even though the microphone 103 is muted, so that the occurrence of echo and howling can be suppressed. Further, since the output of the residual signal E (t) to the coefficient correction circuit 111 is cut off, the update of the transmission coefficient is stopped while the microphone 103 is muted. Therefore, echo and howling can be suppressed quickly after the mute is released.

4. Fourth Embodiment (Configuration of I / O device 1) FIG. 4 is a block diagram of the input / output device 1 according to the fourth embodiment. The difference from the third embodiment of the fourth embodiment is that the adaptive filter circuit 120 includes an output cutoff circuit 116 after the transmission signal output terminal 107. In the following, the differences will be mainly described. Also in this embodiment, it is assumed that the microphone 103 is muted.

The output cutoff circuit 116 is arranged between the transmission signal output terminal 107 and the output terminal 108. When the stop signal is input from the control circuit 115, the output cutoff circuit 116 stops the output of the signal input from the transmission signal output terminal 107. As a result, the output of the residual signal E (t) to the output terminal 108 is stopped while the microphone 103 is muted. When the microphone mute signal is input from the mute signal input unit 114, the control circuit 115 outputs a control signal for stopping the output from the output cutoff circuit 116 to the output cutoff circuit 116. As a result, the signal output from the subtraction circuit 106 is cut off by the output cutoff circuit 116.

In this embodiment, since the control circuit 115 does not stop the processing of the microphone amplifier circuit 104, the product-sum calculation circuit 112, and the subtraction circuit 106, the residual signal E (t) from the subtraction circuit 106 to the output cutoff circuit 116. Is output. Further, in the present embodiment, the route from the subtraction circuit 106 to the coefficient correction circuit 111 is maintained, and the control circuit 115 does not stop the processing of the coefficient correction circuit 111. Therefore, the coefficient correction circuit 111 continues to calculate the update value of the transmission coefficient even while the microphone 103 is muted.

(Action and effect) (1) In the input / output device 1 according to the fourth embodiment, the adaptive filter circuit 120 is generated based on the pseudo echo signal Z (t) and the transmission signal Y (t) when the microphone 103 is muted. The output of the residual signal E (t) is stopped. Specifically, when the microphone mute signal is input from the mute signal input unit 114, the control circuit 115 blocks the signal output from the transmission signal output terminal 107 by the output cutoff circuit 116. Therefore, as in the third embodiment, it is possible to suppress the output of the residual signal E (t) even though the microphone 103 is muted, so that the occurrence of echo and howling can be suppressed.

(2) Further, since the output of the residual signal E (t) to the coefficient correction circuit 111 is not cut off, the coefficient correction circuit 111 continues to calculate the update value of the transmission coefficient even while the microphone 103 is muted. To do. Therefore, the learning function of the transmission coefficient can be continued even during mute. Therefore, even if the arrangement of the speaker 102 and the microphone 103 (that is, the echo path) is changed during mute, echo and howling can be quickly suppressed after the mute is released.

5. Fifth embodiment (Configuration of I / O device 1) FIG. 5 is a block diagram of the input / output device 1 according to the fifth embodiment. The difference from the first embodiment of the fifth embodiment is that the adaptive filter circuit 120 includes an input cutoff circuit 119 in front of the received signal input terminal 109. In the following, the differences will be mainly described. In this embodiment, it is assumed that the speaker 102 is muted.

The input cutoff circuit 119 is arranged between the input terminal 100 and the received signal input terminal 109. When the stop signal is input from the control circuit 115, the input cutoff circuit 119 stops the output of the received signal X (t) input from the input terminal 100. As a result, the generation of the pseudo echo signal Z (t) and the residual signal E (t) is stopped while the speaker 102 is muted. When the speaker mute signal is input from the mute signal input unit 114, the control circuit 115 outputs a control signal for stopping the output from the input cutoff circuit 119 to the input cutoff circuit 119. As a result, the received signal X (t) input from the input terminal 100 is cut off by the input cutoff circuit 119.

In the present embodiment, the control circuit 115 does not stop the processing of the microphone amplifier circuit 104 and the subtraction circuit 106, but the sum of products is obtained by blocking the input of the received signal X (t) to the received signal storage circuit 110. The arithmetic circuit 112 does not work. Therefore, the transmission signal Y (t) is output as it is as the residual signal E (t) from the subtraction circuit 106. Further, in the present embodiment, the control circuit 115 does not stop the processing of the coefficient correction circuit 111, but the coefficient correction circuit 111 is blocked by the input of the received signal X (t) to the coefficient correction circuit 111. It will not work. Therefore, the update of the transmission coefficient by the coefficient correction circuit 111 is stopped. As a result, the transfer coefficient stored in the coefficient storage circuit 113 is retained while the speaker 102 is muted.

(Action and effect) In the input / output device 1 according to the fifth embodiment, the adaptive filter circuit 120 is a residual generated based on the pseudo echo signal Z (t) and the transmission signal Y (t) when the speaker 102 is muted. Stop the output of signal E (t). Specifically, when the speaker mute signal is input from the mute signal input unit 114, the control circuit 115 blocks the received signal X (t) input from the input terminal 100 by the input cutoff circuit 119.

Therefore, as in the first embodiment, it is possible to suppress the output of the residual signal E (t) even though the speaker 102 is muted, so that the occurrence of echo and howling can be suppressed. Further, by blocking the input of the received signal X (t) to the coefficient correction circuit 111, the transmission coefficient stored in the coefficient storage circuit 113 can be retained. Therefore, echo and howling can be suppressed quickly after the mute is released.

(Other embodiments) Although the present invention has been described in accordance with the above embodiments, the statements and drawings that form part of this disclosure should not be understood to limit the invention. Various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art from this disclosure. For example, in the above embodiment, the adaptive filter circuit 120 includes the coefficient correction circuit 111, but the present invention is not limited to this. The adaptive filter circuit 120 does not include the coefficient correction circuit 111, and the coefficient storage circuit 113 may store a fixed value as the transmission coefficient. Even in this case, if the fluctuation of the voice transmission characteristic between the speaker 102 and the microphone 103 is small, the influence on the sound quality is small.

100 input terminal 101 Speaker amplifier circuit 102 speaker 103 microphone 104 Microphone amplifier circuit 105 Transmission signal input terminal 106 Subtraction circuit 107 Transmission signal output terminal 108 Output terminal 109 Earpiece signal input terminal 110 Received signal storage circuit 111 Coefficient correction circuit 112 Multiply-accumulate circuit 113 Coefficient memory circuit 114 Mute signal input terminal 115 control circuit 117 Output cutoff circuit 118 Output cutoff circuit 119 Input cutoff circuit 120 Adaptive filter circuit