JP5923705B2 - Call signal processing device - Google Patents

Description

  The present invention relates to a call signal processing apparatus.

  Conventionally, an apartment intercom that transmits call voice between a dwelling unit installed in each dwelling unit, a common unit device (lobby interphone) installed in a common entrance, and a control room communication device installed in a control room A system is provided. In such an apartment intercom system, a communication device (such as a dwelling unit or a control room communication device) in the system and an external communication device (such as a fixed telephone or a mobile phone) connected to the public telephone network. Some have an external line transfer device (call signal processing device) for transferring voice between them (for example, see Patent Document 1). For example, when a management room call device is called from a dwelling unit while the manager is not present, the outside line transfer device (call signal processing device) transfers the call from the dwelling unit to the manager's mobile phone and carries it with the dwelling unit. The external line transfer device transfers the call voice to and from the telephone. Thereby, the resident and the manager of the dwelling unit can talk using the dwelling unit and the mobile phone.

  By the way, an unpleasant echo may be heard by an acoustic feedback path formed by acoustic coupling between a microphone and a speaker of the external communication device. Alternatively, when a closed loop is formed in the communication system such that the loop gain in an arbitrary frequency component exceeds 1 times by the feedback path or the like, howling may occur at the frequency. In order to prevent such unpleasant echoes and howling from occurring, there is a call signal processing apparatus including an echo canceller, a voice switch, and an echo suppressor (see, for example, Patent Document 1).

  FIG. 12 shows a block diagram of a conventional call signal processing apparatus. This speech signal processing apparatus includes a double talk detecting unit 101, a voice switch 102, an echo suppressor 103, an attenuation setting unit 104, an A / D converter 105, a D / A converter 106, and a two-wire four. A line conversion unit 107 and a transmission unit 108 are provided. The transmission unit 108 is connected to a call device (such as a dwelling unit or a control room call device) via a signal line L, and performs packet transmission with the call signal processing device.

  The transmission unit 108 divides the received signal (received voice data) output from the echo suppressor 103 to create a packet, encodes the packet (voice packet), and converts the encoded bit string into an electrical signal ( Modulated) and sent to the signal line L. The transmission unit 108 converts (modulates) an electric signal transmitted from the signal line L into a bit string, decodes a voice packet from the demodulated bit string, and decodes a transmitted signal (transmitted voice data). Is output to the D / A converter 106. Then, the transmission signal modulated into an analog signal by the D / A converter 106 is output to the 2-wire 4-wire conversion unit 107. The two-wire / four-wire conversion unit 107 is connected to the public telephone network by a local line (telephone line) Lx, and transmits a transmission signal to the telephone line Lx, and receives a reception signal transmitted through the telephone line Lx as A. / D converter 105 to output. The received signal is converted into a digital signal (received voice data) by the A / D converter 105 and input to the echo suppressor 103.

  The voice switch 102 always estimates the call state (sending state, receiving state), and inserts losses into the signal paths on the transmitting side and the receiving side with an appropriate distribution based on the estimation result. In addition, the voice switch 102 outputs the estimated call state to the attenuation amount setting unit 104.

  The double talk detecting unit 101 detects whether or not the speaker who talks with the external communication device F and the speaker who talks with the dwelling unit communication device A are in a double talk state. Then, the double talk detection unit 1 outputs the double talk detection result to the attenuation amount setting unit 4.

  The attenuation amount setting unit 104 calculates an attenuation amount to be set in the echo suppressor 103 based on both the detection result of the double talk detection unit 101 and the estimation result of the voice switch 102.

  The echo suppressor 103 inserts the attenuation amount set by the attenuation amount setting unit 104 into the reception side signal path, and suppresses the echo by attenuating the reception signal.

JP 2010-273316 A

In the conventional call signal processing apparatus described above, the attenuation amount setting unit 104 determines the attenuation amount in conjunction with both the voice switch 102 and the double talk detection unit 101. Therefore, if the speech signal processing apparatus which is not provided with a voice switch 10 2 is provided an echo suppressor 103, it is necessary to newly add a voice switch, there is a problem that the processing amount increases.

  The present invention has been made in view of the above reasons, and an object thereof is to provide a call signal processing apparatus capable of realizing echo suppression by an echo suppressor even when a voice switch is not provided. It is in.

  The speech signal processing apparatus of the present invention includes a reception side signal path for transmitting a reception signal from a telephone terminal, a transmission side signal path for transmitting a transmission signal to the telephone terminal, the reception side signal path, and the transmission A double talk detecting unit for detecting a double talk state in which a signal is simultaneously transmitted to the side signal path; a first level calculating unit for calculating a signal level of the transmitting side signal path; and an echo suppressor for attenuating the received signal. And an attenuation amount setting unit that sets an attenuation amount to be attenuated by the echo suppressor, wherein the attenuation amount setting unit includes a detection result of the double talk detection unit and the first level calculation unit. The attenuation amount is calculated based on the calculation result.

  In this call signal processing apparatus, the attenuation amount setting unit is provided only when the double talk detection unit does not detect double talk and the calculation result of the first level calculation unit is equal to or greater than a first threshold value. The attenuation is preferably set to a predetermined value greater than zero.

  The speech signal processing apparatus includes a second level calculation unit that calculates a signal level of the receiver signal path, and the attenuation setting unit includes a detection result of the double talk detection unit, and the first and second levels. It is preferable to calculate the amount of attenuation based on each calculation result of the level calculation unit.

In the speech signal processing device, the attenuation setting unit includes a first value in which the double talk detection unit does not detect double talk and the calculation result of the first level calculation unit is equal to or greater than a first threshold value. In the state, the attenuation amount is set to a predetermined value larger than zero, the calculation result of the first level calculation unit is less than the first threshold value, and the calculation result of the second level calculation unit is When the second state is equal to or greater than a second threshold, the attenuation amount is changed to zero with a first time constant, and the calculation result of the first level calculation unit is equal to or greater than the first threshold. In addition, when the calculation result of the second level calculation unit is equal to or greater than the second threshold value and the double talk detection unit is in the third state in which double talk is detected, the attenuation amount is set to the first amount. Zero with a second time constant greater than It is dynamic,
When the combination of the detection result of the double-talk detection unit and the calculation results of the first and second level calculation units is other than the first to third states, the attenuation amount is set to the second time. It is preferable to change to zero with a third time constant larger than the constant.

  In the speech signal processing device, the double talk detection unit may detect double talk based on a ratio between a calculation result of the first level calculation unit and a calculation result of the second level calculation unit. preferable.

  The speech signal processing apparatus includes an echo canceller provided in a preceding stage of the second level calculation unit and configured to suppress an echo generated when the transmitted signal wraps around the receiver signal path due to acoustic coupling of the speech terminal. It is preferable.

  The speech signal processing apparatus includes an echo canceller provided at a subsequent stage of the second level calculation unit and configured to suppress an echo generated when the transmission signal wraps around the reception-side signal path due to acoustic coupling of the communication terminal. It is preferable.

  In the speech signal processing apparatus, it is preferable that the double talk detector calculates a correlation value between the received signal and the transmitted signal and detects double talk based on the correlation value.

  In the speech signal processing apparatus, it is preferable that the double talk detector calculates a different code rate between the received signal and the transmitted signal and detects double talk based on the different code rate.

  The call signal processing apparatus preferably includes an echo canceller that suppresses an echo generated when the transmitted signal wraps around the signal path on the receiver side due to acoustic coupling of the call terminal, and includes the double talk detector.

  In this call signal processing device, it is preferable that the first level calculation unit calculates a signal level from an average of absolute values of the transmission signals.

  The speech signal processing apparatus includes a second level calculation unit that calculates a signal level of the reception side signal path, and the second level calculation unit calculates a signal level from an average of absolute values of the reception signals. It is preferable.

  In this call signal processing apparatus, it is preferable that the attenuation amount setting unit increases the attenuation amount as the calculation result of the first level calculation unit increases.

  In this speech signal processing device, an adaptive filter for adaptively identifying a characteristic of an echo path that is generated when the transmitted signal wraps around the receiver signal path due to acoustic coupling of the speech terminal, and the adaptive filter from the received signal It is preferable to include an echo canceller having a subtractor for subtracting the output of the output, and the attenuation amount setting unit sets the attenuation amount based on a coefficient of the adaptive filter.

  As described above, the present invention has an effect that the echo suppression by the echo suppressor can be realized even when the voice switch is not provided.

It is a block diagram which shows the structure of the external line transfer apparatus of Embodiment 1 of this invention. It is a system block diagram of the intercom system for apartment houses containing the external line transfer apparatus same as the above. It is a graph which shows the attenuation amount with respect to the calculation result of a 1st level calculation part. It is a block diagram which shows the structure of the external line transfer apparatus of Embodiment 2. It is a graph which shows the fluctuation | variation of attenuation amount. It is a table | surface which shows the combined state of the calculation result of a 1st, 2nd level calculation part, and the detection result of a double talk detection part. It is a block diagram which shows the structure of the external line transfer apparatus of Embodiment 3. It is a block diagram which shows another structure same as the above. It is a block diagram which shows another structure same as the above. It is a block diagram which shows the structure of the external line transfer apparatus of Embodiment 4. FIG. 10 is a block diagram illustrating a configuration of an external line transfer device according to a fifth embodiment. It is a block diagram which shows the structure of the conventional external line transfer apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 2 shows a system configuration example of an intercom system for apartment houses including the external line transfer device E of the present embodiment (corresponding to the call signal processing device of the present invention). This intercom system for collective housing is composed of a plurality of units (only one in the figure) dwelling unit communication device A installed in each dwelling unit of the condominium and a common unit communication device (not shown) installed in the common entrance of the collective housing. , Main line control device B, management room communication device C, and the like.

  Each dwelling unit communication device A is branched and connected to the trunk line L1 via the dwelling unit separate line L2 and the branching unit D. The trunk line L1 is connected to the trunk line control device B, and a plurality (only one in the figure) of branching devices D are provided on the trunk line L1. Further, a management room call device C is connected to the main line control device B via a signal line L3. The management room call device C is installed in the management room of the apartment house, and is used when the manager calls the resident of each dwelling unit.

  In the intercom system for apartment houses in this embodiment, digitally modulated audio information (audio data), video information (video data), and control information (control data) are transmitted through transmission lines (main line L1, dwelling line L2, signal line L3). , L4). For example, in a common area communication device (lobby intercom), when a visitor accepts an operation input of a dwelling unit number of any dwelling unit by operating a numeric keypad or a touch panel, a packet storing the dwelling unit number in a data field and imaging A packet in which a video (video data) of a visitor imaged by the apparatus is stored in a data field is transmitted (packet transmission) to the address of the trunk control apparatus B via a signal line. The main line control device B sends a control packet storing a call command for notifying a call from the lobby intercom in the data field and a video packet storing the video data in the data field to the main line L1. When the control unit and the video packet are received via the trunk line L1 and the unit-specific line L2, the unit communication device A installed in the unit with the unit number receives a call command (control signal) stored in the data field of the control packet. ) To ring from the speaker. Further, the video data stored in the data field of the video packet is processed to display the video of the visitor on a display device such as a liquid crystal display. When a resident who has heard the ringing tone operates a response button (not shown) of the dwelling unit communication apparatus A, a voice signal (sending signal) output from the microphone is packet-transmitted via the dwelling unit separate line L2. Similarly, also in the lobby intercom, a voice signal (transmission signal) output from the microphone is packet-transmitted to the dwelling unit communication device A via the trunk line control device B. As a result, a resident of the dwelling unit and a visitor can make an interphone call using the dwelling unit call device A and the lobby intercom.

  In addition, the management room call device C can be called from the dwelling unit call device A, and the resident and the manager can talk using the dwelling unit call device A and the control room call device C. In this case, a packet including control data for calling the control room call device C from the dwelling unit call device A is transmitted, and the packet is transmitted to the control room call device C via the trunk line control device B. When the handset of the control room call device C is off-hook (or the call button is operated), voice data is transferred between the dwelling unit call device A and the control room call device C as in the case of the lobby intercom. Packets are transmitted to each other. However, since the dwelling unit call device A, the main line control device B, the lobby intercom, and the management room call device C described above can be realized by using a conventionally known technique, detailed illustration and description of the configuration are omitted.

  Here, when a call is made from the dwelling unit call device A to the control room call device C while the manager is absent, the call of the dwelling unit call device A is transferred to the mobile phone possessed by the manager or the reception center of the management company. . Then, it is desirable to be able to talk by transmitting voice between a call terminal such as a transfer destination mobile phone or a reception center phone (hereinafter referred to as an external call device F) and the dwelling unit call device A. . For this purpose, the intercom system for collective housing in this embodiment includes an external line transfer device E that transfers audio between the dwelling unit call device A and the external call device F.

  As shown in FIG. 1, the external line transfer device E includes a double talk detection unit 1, a first level calculation unit 2, an echo suppressor 3, an attenuation setting unit 4, an A / D converter 5, a D / D converter An A converter 6, a two-wire / four-wire converter 7, and a transmitter 8 are provided. The transmission unit 8 is connected to the trunk line control apparatus B via the signal line L4, and performs packet transmission with the dwelling unit call apparatus A via the trunk line control apparatus B.

  The transmission unit 8 divides the received signal (received voice data) output from the echo suppressor 3 to create a packet, encodes the packet (voice packet), and converts the encoded bit string into an electric signal ( Modulated) and sent to the signal line L4. The transmission unit 8 converts (modulates) the electric signal transmitted from the signal line L4 into a bit string, and transmits a transmission signal (transmission voice data) obtained by decoding a voice packet from the demodulated bit string. The signal is output to the D / A converter 6 via a path (lower signal path in FIG. 1). Then, the transmission signal modulated into an analog signal by the D / A converter 6 is output to the 2-wire 4-wire conversion unit 7. The two-wire / four-wire conversion unit 7 is connected to the public telephone network N by a station line (telephone line) Lx, and transmits a transmission signal to the telephone line Lx and receives a reception signal transmitted through the telephone line Lx. Output to the A / D converter 5. The received signal is converted into a digital signal (received voice data) by the A / D converter 5 and input to the echo suppressor 3 through the received signal path (upper signal path in FIG. 1).

  The double-talk detection unit 1 is configured such that a signal is transmitted simultaneously to the transmission side signal path and the reception side signal path, that is, a speaker who makes a call with the external communication device F and a speaker who makes a call with the dwelling unit communication device A simultaneously. Detect whether or not you are in a talking double talk state. Then, the double talk detection unit 1 outputs the double talk detection result to the attenuation amount setting unit 4.

  The first level calculation unit 2 calculates a voice level (signal level) of a transmission signal (transmission voice data). Then, the first level calculation unit 2 outputs the signal level calculation result of the transmission signal to the attenuation amount setting unit 4. Specifically, the first level calculation unit 2 calculates the average value (short-time average value) of the absolute value of the transmission signal in a relatively short time and outputs it to the attenuation amount setting unit 4.

  In general, it is considered that the level of the short-time average value is determined mainly by the voice component included in the input signal (speech signal). On the other hand, the average value (long-term average value) of the input signal over a relatively long time is determined mainly by the noise component (sound component other than voice) contained in the input signal (speech signal). It is considered.

  Therefore, the first level calculation unit 2 performs arithmetic processing of the following formula (1) or formula (2) in order to calculate the level of the voice component included in the transmission signal, and calculates the absolute value of the transmission signal. A short-time average value L (n) is calculated. It is assumed that the absolute value of the transmission signal is x (n) and the average number of samples is M.

  Then, the first level calculation unit 2 outputs the calculated short-term average value L (n) of the absolute value of the transmission signal to the attenuation amount setting unit 4 as a signal level calculation result of the transmission signal. As described above, the first level calculation unit 2 can calculate the signal level of the transmission signal by a simple calculation.

  The attenuation amount setting unit 4 calculates the attenuation amount to be set in the echo suppressor 3 based on the detection result of the double talk detection unit 1 and the calculation result of the first level calculation unit 2.

  The echo suppressor 3 attenuates the reception signal by inserting the attenuation amount set by the attenuation amount setting unit 4 into the reception side signal path.

  Below, the calculation method of the attenuation amount which the attenuation amount setting part 4 sets to the echo suppressor 3 is demonstrated.

  The attenuation amount setting unit 4 has a first threshold value set in advance, and compares the first threshold value with the calculation result of the first level calculation unit 2. Then, the attenuation amount setting unit 4 calculates the attenuation amount based on both the comparison result between the calculation result of the first level calculation unit 2 and the first threshold and the double talk detection result of the double talk detection unit 1. To do. Specifically, the attenuation amount setting unit 4 includes, in the received signal, when the calculation result of the first level calculation unit is equal to or greater than the first threshold value and the double talk detection unit 1 does not detect double talk. It is determined that the voice of the speaker who uses the external call device F is not included. Then, the attenuation amount setting unit 4 sets the attenuation amount to a predetermined value greater than zero. As a result, even when the signal level of the transmission signal is high and an echo is generated in which the transmission signal wraps around the reception-side signal path due to the acoustic coupling between the microphone and the speaker of the external communication device F (call terminal), the echo suppressor 3 can attenuate the received signal and suppress the echo.

  On the other hand, when the calculation result of the first level calculation unit is less than the first threshold, the attenuation amount setting unit 4 determines that the signal level of the transmission signal is low and that the echo by the external communication device F is not present or small. To do. In addition, when the double talk detecting unit 1 detects double talk, the attenuation amount setting unit 4 determines that the voice of the speaker using the external call device F is included in the received signal. Accordingly, the attenuation amount setting unit 4 sets the attenuation amount to zero when the calculation result of the first level calculation unit is less than the first threshold value or when the double talk detection unit 1 detects double talk. To do. Thereby, since the echo suppressor 3 does not attenuate the reception signal, the reception volume can be prevented from being suppressed.

  That is, only when the signal level of the transmitted signal is high, the echo is suppressed by attenuating the received signal with the echo suppressor 3, and in other cases, the received signal is not attenuated. Therefore, the voice of the speaker used by the external communication device F is not attenuated due to erroneous attenuation. Furthermore, the echo suppressor 3 does not erroneously insert an attenuation amount and does not generate an unpleasant echo. As a result, a simultaneous call in which only an unpleasant echo is attenuated is possible, and as a result, a comfortable call environment can be provided.

  As described above, in the present embodiment, low processing using only the detection result of the double talk detection unit 1 and the calculation result of the first level calculation unit 2 without providing a voice switch unlike the conventional call signal processing device. The amount of attenuation set in the echo suppressor 3 can be controlled by the amount, and the echo can be suppressed.

  In addition, there are the following methods for the double talk detector 1 to detect double talk.

  The double talk detector 1 calculates a correlation value between the transmission signal and the reception signal, and compares the correlation value with a predetermined threshold value to determine whether or not the double talk state is set. When the calculated correlation value is high and equal to or greater than the threshold value, the double talk detecting unit 1 determines that the received signal is dominated by the echo component from the external communication device F and is not in the double talk state. On the other hand, when the calculated correlation value is low and less than the threshold value, the double-talk detector 1 is in a double-talk state because the voice component of the speaker using the external communication device F is dominant in the received signal. Judge.

  In this way, the double talk detector 1 can estimate double talk with high accuracy based on the correlation value between the transmitted signal and the received signal.

  Further, the double talk detecting unit 1 calculates a different code rate between the transmitted signal and the received signal (a ratio in which the codes of the transmitted signal and the received signal are different), and compares the different code rate with a predetermined threshold value. Thus, it may be determined whether or not the state is a double talk state. When the calculated different code rate is low and less than the threshold value, the double talk detector 1 determines that the echo signal from the external communication device F is dominant in the received signal and is not in the double talk state. On the other hand, when the calculated different code rate is high and equal to or greater than the threshold value, the double-talk detector 1 is dominated by the voice component of the speaker using the external call device F, and in the double-talk state. Judge that there is.

  As described above, the double talk detector 1 can estimate double talk with high accuracy based on the different code rates of the transmission signal and the reception signal. Further, the transmission signal and the reception signal are composed of digital signals, and the double talk detector 1 can calculate the different code rate with a low processing amount, and can easily estimate the double talk.

  Further, the attenuation amount setting unit 4 may be configured to vary the attenuation amount set in the echo suppressor 3 based on the calculation result of the first level calculation unit 2.

  FIG. 3 shows a graph of attenuation with respect to the calculation result of the first level calculation unit 2. The attenuation amount setting unit 4 calculates the attenuation amount based on the calculation result of the first level calculation unit 2. Specifically, as shown in FIG. 3, the attenuation amount setting unit 4 increases the attenuation amount as the calculation result of the first level calculation unit 2 increases. That is, the attenuation amount setting unit 4 is configured to determine that the echo component included in the received signal also increases as the transmission volume increases, and to further suppress the echo component by increasing the attenuation amount.

  As described above, the attenuation amount setting unit 4 adjusts the attenuation amount based on the calculation result of the first level calculation unit 2, so that even when the received signal is erroneously attenuated by the echo suppressor 3, voice suppression is performed. Can be minimized.

  In the present embodiment, the call signal processing device of the present invention is applied to the external line transfer device E of the intercom system for collective housing, but the present invention is not limited to this. For example, the call signal processing device of the present invention may be applied to a call device (call terminal) such as an interphone master / slave device or telephone.

(Embodiment 2)
FIG. 4 shows a block configuration diagram of the external line transfer apparatus E of the present embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to the external line transfer apparatus E of Embodiment 1, and description is abbreviate | omitted. The present embodiment is characterized in that a second level calculation unit 9 is provided.

  The second level calculation unit 9 calculates the voice level (signal level) of the received signal (received voice data). The second level calculation unit 9 has the same configuration as the first level calculation unit 2 and calculates a short-time average value of the absolute value of the received signal (see equations (1) and (2)). . Then, the second level calculation unit 9 outputs the calculated short-term average value of the absolute value of the received signal to the attenuation amount setting unit 4 as a signal level calculation result of the received signal. In this way, the second level calculation unit 9 can calculate the signal level of the received signal by a simple calculation.

  Then, the attenuation amount setting unit 4 includes the detection result of the double talk detection unit 1, the comparison result between the calculation result of the first level calculation unit 2 and the first threshold, the second level calculation unit 9, and the second level calculation unit 9. The amount of attenuation and the time constant for varying the amount of attenuation are determined based on the comparison result with the threshold value. The attenuation amount calculated by the attenuation amount setting unit 4 will be described with reference to FIGS.

  As shown in FIG. 5, before time t0, a first state in which the calculation result of the first level calculation unit 2 is equal to or greater than the first threshold and the double talk detection unit 1 is not detecting double talk. (See Y1 in FIG. 6), and the attenuation amount setting unit 4 sets the attenuation amount to a maximum value (Max) that is a predetermined value larger than zero.

  At time t0, the calculation result of the first level calculation unit 2 is greater than or equal to the first threshold, the calculation result of the second level calculation unit 9 is greater than or equal to the second threshold, and the double talk detection unit Assume that 1 changes to the third state (see Y3 in FIG. 6) in which double talk is detected. In this case, the attenuation amount setting unit 4 changes the attenuation amount to zero (0 dB) with the second time constant. Specifically, as shown by a solid line Y3 in FIG. 5, the attenuation amount setting unit 4 varies the attenuation amount from the maximum value to zero over a period (tens of milliseconds) from time t0 to t2.

  Here, at time t1 in the period from time t0 to time t2, the calculation result of the first level calculation unit 2 is less than the first threshold value, and the calculation result of the second level calculation unit 9 is the second value. Assume that the state has changed to the second state (see Y2 in FIG. 6) that is above the threshold. In this case, the attenuation amount setting unit 4 changes the attenuation amount to zero with a first time constant smaller than the second time constant. Specifically, as shown by a broken line Y2 in FIG. 5, the attenuation amount setting unit 4 instantaneously varies the attenuation amount to zero.

  Further, at time t0, it is assumed that the combination of the detection result of the double talk detection unit 1 and the calculation results of the first and second level calculation units 2 and 9 has changed to a state other than the first to third states. . Examples of states other than the first to third states include the following states (see Y4 in FIG. 6). The calculation result of the first level calculation unit 2 is less than the first threshold value, the calculation result of the second level calculation unit 9 is less than the second threshold value, and the double talk detection unit 1 detects no double talk. The state that is. Alternatively, the calculation result of the second level calculation unit 9 is less than the second threshold, and the double talk detection unit 1 detects double talk. In this case, the attenuation amount setting unit 4 changes the attenuation amount to zero with a third time constant larger than the second time constant. Specifically, as indicated by a broken line Y4 in FIG. 5, the attenuation amount setting unit 4 varies the attenuation amount from the maximum value to zero over a period (several hundred milliseconds) from time t0 to t4.

  Here, at time t3 in the period from time t0 to time t4, the calculation result of the first level calculation unit 2 is greater than or equal to the first threshold value, and the double talk detection unit 1 is the first in which double talk is not detected. (See Y1 in FIG. 6). In this case, as indicated by a broken line Y1 in FIG. 5, the attenuation amount setting unit 4 instantaneously varies the attenuation amount to the maximum value.

  Thus, in the present embodiment, the attenuation amount is calculated based on the detection result of the double talk detection unit 1 and the calculation results of the first and second level calculation units 2 and 9, and the calculated attenuation amount varies. The time constant is adjusted. That is, by adjusting the time constant of the amount of attenuation to be changed according to the call state, unnatural suppression by the echo suppressor 3 during a call can be suppressed, and a comfortable call environment can be provided.

(Embodiment 3)
FIG. 7 shows a block diagram of the external line transfer apparatus E of the present embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 1, 2, and description is abbreviate | omitted. In the present embodiment, the double talk detection unit 1 is configured to receive the calculation results of the first and second level calculation units 2 and 9.

  The double talk detection unit 1 of the present embodiment calculates the ratio of the calculation result of the second level calculation unit 9 to the calculation result of the first level calculation unit 2, and compares the calculated ratio with the third threshold value. The double talk is detected from the comparison result. The double talk detection unit 1 determines that the state is a double talk state when (calculation result of the second level calculation unit 9) / (calculation result of the first level calculation unit 2) ≧ third threshold value. The double-talk detection unit 1 is in a non-double-talk state when (calculation result of the second level calculation unit 9) / (calculation result of the first level calculation unit 2) <third threshold value. judge.

  With this configuration, the double talk detector 1 does not need to include a detector that detects the signal levels of the transmitted signal and the received signal, and can detect double talk with a simple configuration.

  As shown in FIGS. 8 and 9, an echo canceller 10 that suppresses echoes due to acoustic coupling of the external communication device F may be provided.

  The echo canceller 10 has a conventionally known configuration including an adaptive filter and a subtracter (not shown), and adaptively identifies the impulse response of the feedback path formed by the acoustic coupling of the external communication device F by the adaptive filter. Then, the echo component estimated from the transmission signal input to the D / A converter 6 is subtracted from the reception signal output from the A / D converter 5 by the subtractor to suppress the echo.

  As shown in FIG. 8, by providing the echo canceller 10 in front of the second level calculation unit 9, the second level calculation unit 9 calculates the signal level of the received signal whose echo is suppressed by the echo canceller 10. can do. Thereby, the detection accuracy of the signal level of the received signal and the detection accuracy of the double talk detector 1 can be improved.

  However, when the echo canceller 10 is provided before the second level calculation unit 9, the calculation result of the second level calculation unit 9 varies depending on the convergence state of the adaptive filter. Therefore, the second threshold value to be compared with the calculation result of the second level calculation unit 9 and the ratio of the calculation result of the second level calculation unit 9 to the calculation result of the first level calculation unit 2 are compared with the third threshold value. The threshold needs to be set in consideration of the convergence status of the adaptive filter. Therefore, as shown in FIG. 9, by providing an echo canceller 10 subsequent to the second level calculation unit 9, the second threshold value and the third threshold value can be set regardless of the convergence state of the adaptive filter. .

(Embodiment 4)
FIG. 10 shows a block configuration diagram of the external line transfer apparatus E of the present embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 1-3, and description is abbreviate | omitted. The present embodiment is characterized in that an echo canceller 10 including a double talk detector 1 is provided.

  The attenuation amount setting unit 4 calculates the attenuation amount to be set in the echo suppressor 3 based on the calculation result of the first level calculation unit 2 and the detection result of the double talk detection unit 1 built in the echo canceller 10. . Note that the control of the attenuation amount setting unit 4 is the same as that of the first embodiment, and a description thereof will be omitted.

  As described above, when the echo canceller 10 including the double talk detection unit 1 is provided, the attenuation amount setting unit 4 uses the detection result to set the attenuation amount to the double talk detection unit 1 included in the echo canceller 10. calculate. Therefore, it is not necessary to provide the double talk detector 1 separately, and the configuration can be simplified.

(Embodiment 5)
FIG. 11 shows a block diagram of the external line transfer apparatus E of the present embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to Embodiment 1-4, and description is abbreviate | omitted. In the present embodiment, the attenuation amount setting unit 4 is characterized in that the set attenuation amount is adjusted based on the coefficient of the adaptive filter included in the echo canceller 10.

  The attenuation amount setting unit 4 estimates the echo by the external communication device F by performing Fourier transform on the filter coefficient of the adaptive filter, and sets the attenuation amount according to the estimated echo. For example, when the estimated echo is large, the attenuation is increased, and when the estimated echo is small, the attenuation is also decreased. Then, when the update of the filter coefficient is stopped, the attenuation amount setting unit 4 determines that there is no echo in the received signal or is small, and reduces the attenuation amount.

  Thus, in the present embodiment, when the attenuation amount setting unit 4 sets an attenuation amount larger than zero in the echo suppressor 3, the attenuation amount is adjusted according to the state of the echo canceller 10 to obtain an optimal attenuation amount. Can be set in the echo suppressor 3.

DESCRIPTION OF SYMBOLS 1 Double talk detection part 2 1st level calculation part 3 Echo suppressor 4 Attenuation amount setting part 5 A / D converter 6 D / A converter 7 2 line | wire 4 line conversion part 8 Transmission part

Claims (14)

A receiver signal path for transmitting a reception signal from a call terminal;
A transmission side signal path for transmitting a transmission signal to the call terminal;
A double-talk detector for detecting a double-talk state in which signals are simultaneously transmitted to the receiver-side signal path and the transmitter-side signal path;
A first level calculation unit for calculating a signal level of the transmission side signal path;
An echo suppressor for attenuating the received signal;
The echo suppressor comprises an attenuation amount setting unit for setting an attenuation amount to be attenuated by the echo suppressor,
The call signal processing apparatus, wherein the attenuation amount setting unit calculates the attenuation amount based on a detection result of the double talk detection unit and a calculation result of the first level calculation unit.   The attenuation amount setting unit sets the attenuation amount to zero only when the double talk detection unit does not detect double talk and the calculation result of the first level calculation unit is equal to or greater than a first threshold value. 2. The call signal processing apparatus according to claim 1, wherein a large predetermined value is set. A second level calculator for calculating a signal level of the receiver signal path,
The attenuation amount setting unit calculates the attenuation amount based on a detection result of the double talk detection unit and calculation results of the first and second level calculation units. 3. The call signal processing device according to 2. The attenuation setting unit
When the double talk detection unit does not detect double talk and the calculation result of the first level calculation unit is in a first state that is equal to or greater than a first threshold, the attenuation amount is a predetermined value greater than zero. Set to
When the calculation result of the first level calculation unit is less than the first threshold value and the calculation result of the second level calculation unit is a second state in which the calculation result is equal to or greater than the second threshold value, the attenuation amount To zero with the first time constant,
The calculation result of the first level calculation unit is not less than the first threshold, the calculation result of the second level calculation unit is not less than the second threshold, and the double talk detection unit is double talk. When the third state is detecting, the attenuation amount is changed to zero with a second time constant larger than the first time constant,
When the combination of the detection result of the double-talk detection unit and the calculation results of the first and second level calculation units is other than the first to third states, the attenuation amount is set to the second time. 4. The speech signal processing apparatus according to claim 3, wherein the call signal processing device is changed to zero with a third time constant larger than the constant.   The double talk detecting unit detects double talk based on a ratio between a calculation result of the first level calculation unit and a calculation result of the second level calculation unit. 4. The call signal processing device according to 4.   The echo canceller is provided in a preceding stage of the second level calculation unit and suppresses an echo generated when the transmission signal wraps around the signal path on the receiving side due to acoustic coupling of the call terminal. The speech signal processing apparatus according to any one of 3 to 5.   The echo canceller is provided at a subsequent stage of the second level calculation unit and suppresses an echo generated when the transmission signal wraps around the signal path on the receiving side due to acoustic coupling of the call terminal. The speech signal processing apparatus according to any one of 3 to 5.   5. The double talk detection unit according to claim 1, wherein the double talk detection unit calculates a correlation value between the reception signal and the transmission signal, and detects double talk based on the correlation value. The call signal processing device according to 1.   5. The double talk detector according to claim 1, wherein the double talk detector calculates a different code rate between the received signal and the transmitted signal, and detects double talk based on the different code rate. 6. The speech signal processing apparatus according to item 1.   10. An echo canceller having the double-talk detection unit is provided, wherein echoes generated when the transmitted signal wraps around the receiver signal path due to acoustic coupling of the call terminal are suppressed. The call signal processing device according to any one of the above.   11. The call signal processing apparatus according to claim 1, wherein the first level calculation unit calculates a signal level from an average of absolute values of the transmission signals. A second level calculator for calculating a signal level of the receiver signal path,
The call signal processing apparatus according to claim 1, wherein the second level calculation unit calculates a signal level from an average of absolute values of the received signal.   13. The call signal processing device according to claim 1, wherein the attenuation amount setting unit increases the attenuation amount as a calculation result of the first level calculation unit increases. . An adaptive filter for adaptively identifying a characteristic of an echo path generated when the transmitted signal wraps around the receiver signal path by acoustic coupling of the call terminal, and a subtractor for subtracting the output of the adaptive filter from the received signal And an echo canceller having
The call signal processing apparatus according to claim 1, wherein the attenuation amount setting unit sets the attenuation amount based on a coefficient of the adaptive filter.

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