JP3253646B2 - Voice communication device and acoustic echo canceller training method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice communication apparatus having an acoustic echo canceller for canceling an acoustic echo generated during a hands-free call, such as an automobile radio telephone apparatus, and an operating state of the acoustic echo canceller. Training method for initial settings.

[0002]

2. Description of the Related Art Conventionally, some radio telephones mounted on a vehicle, such as an automobile radio telephone, are provided with a hands-free communication mode in addition to a handset communication mode.
Hands-free call mode means that a speaker for receiving and a microphone for transmitting are provided on a communication device or dashboard separately from the handset, and these speakers and microphones can be used as a handset to make a call. It was done. With this hands-free call mode, the speaker can talk without having to hold the handset. Significantly useful.

[0003] However, when such a hands-free call mode is used, a received voice output from a speaker goes around the microphone during a call, and is transmitted to the other party to generate an acoustic echo. Therefore, this type of telephone device is generally provided with an echo canceller for canceling the acoustic echo. Such an acoustic echo canceller is indispensable for a radio telephone apparatus for digitizing and transmitting an audio signal, especially since a signal delay due to a codec or the like is large.

FIG. 6 shows an example of the configuration of this type of echo canceller. This echo canceller 10 '
Has an adaptive filter 11, an adder 12, and a RAM 13 for storing cancellation information. Part of the received voice output from the speaker 22 is input to the microphone 23 as an acoustic echo EC, and the echo signal is converted to an A / D signal.
After being converted into a digital signal by the converter 21S and input to the echo canceller 10 ', the echo signal ES
Is supplied to the adaptive filter 11 as a residual signal TS via the adder 12. The adaptive filter 11 performs an adaptive operation for reducing the residual signal TS to zero. The adaptive operation estimates the acoustic characteristics of the used space, that is, the echo path, and based on the estimation result and the received signal RS. A pseudo echo signal EES is generated. In the adder 12,
An arithmetic process for subtracting the pseudo echo signal EES from the echo signal ES is performed, thereby canceling the echo signal ES.

In order to operate the echo canceller 10 'effectively, prior to use, the echo canceller 10' is trained to estimate the acoustic characteristics of the used space, that is, the echo path, and based on the estimation result. To create acoustic echo cancellation information and RAM1
3 must be stored in advance. Therefore, conventionally, for example, training of the echo canceller 10 'is performed as follows.

That is, for example, in the case of an automobile radio telephone device, the user operates the training keys when the acoustic characteristics in the vehicle change, such as when a passenger joins the vehicle during or on the way. . Then, under the control of the control circuit of the wireless telephone device, the changeover switch 14 is switched to connect the training signal generator 16 to the speaker 22. Then, in this state, the training signal generator 1
6, a training signal is generated, and the sound of the training signal is output from the speaker 22. In this state, the echo canceller 10 'performs an adaptation operation for estimating the echo path in the used space based on the training sound. Then, information for canceling the acoustic characteristics in the vehicle is generated based on the estimation result, and the cancellation information is stored in the RAM 13.

[0007] If training is performed in advance before use, the echo canceller 10 ′ can use the RAM 13.
In accordance with the cancellation information stored in the communication device, the optimum echo signal ES is canceled immediately after the start of the call, thereby enabling a high-quality call.

[0008]

However, the apparatus employing such a conventional training method has the following problems to be solved. (1) The user must manually operate the training key to train the echo canceller 10 '. Therefore, the operation is troublesome.

(2) Even if training is performed once, if the number of people in the vehicle changes after that, for example, the acoustic characteristics of the space used change, so that the echo signal ES cannot be canceled properly. Therefore, the user must re-train the echo canceller 10 'by operating the training key each time the number of persons in the vehicle changes or the like. For this reason, the operation is extremely troublesome, and often the training is forgotten. If the training is forgotten, the echo signal ES that has not been completely canceled is sent to the other party as a transmission signal during the period from the start of the call to the stabilization of the echo canceller 10 ', and the call quality deteriorates. Is very undesirable.

(3) In order to prevent the cancellation information stored in the RAM 13 from being erased due to the power cut-off of the apparatus due to the stop of the engine of the car or the like, the RAM 13 needs to be provided with a backup power supply 15. For this reason, the circuit configuration of the echo canceller 10 'is complicated and large. If the backup power supply 15 is not provided, the user must operate the training key to train the echo canceller 10 'every time the engine of the vehicle is started, which further complicates the operation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to reduce the operational burden on the user by completely eliminating the operation for training, and to reduce the sound in the used space. Even if the characteristics change or the power is turned off, the operation state of the echo canceller can always be set to the optimum state without the need for training operation or backup power supply, thereby improving the call quality and the circuit It is an object of the present invention to provide a voice communication device and a method for training an acoustic echo canceller that can achieve a simple miniaturization.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides, separately from a handset, a speaker for loudspeaking and outputting a received voice signal and a microphone for collecting a transmission sound and outputting a transmission signal. A voice communication device comprising means for making a hands-free call using the speaker and the microphone, wherein the sound output from the speaker is canceled by an acoustic echo generated when the sound is input to the microphone. An acoustic echo canceller and training means for the acoustic echo canceller are provided, and the training means trains the acoustic characteristics of the acoustic echo canceller based on a predetermined notification sound output from the speaker during communication path connection control. Things.

Further, the present invention determines whether a call mode using a handset or a hands-free call mode is selected during training.
When the call mode using the handset is selected, this call mode is changed to the hands-free call mode at least during the training period, a predetermined sound is output from the speaker, and the acoustic characteristics of the acoustic echo canceller are determined based on the sound. Training is the feature.

[0014] Further, the present invention, apart from the handset,
A voice communication device comprising: a speaker that outputs a received voice signal and a microphone that collects a transmission sound and outputs a transmission signal; and a unit that performs a hands-free call using the speaker and the microphone. An acoustic echo canceller for canceling an acoustic echo generated when the sound output from the speaker is input to the microphone, and training means for the acoustic echo canceller, and at least one of an operation related to calling and an operation related to incoming call In response, the training means outputs a sound including a frequency component necessary for training from the speaker during the communication path connection control, and trains the acoustic characteristics of the acoustic echo canceller based on the sound. Things.

[0015]

As a result, according to the present invention, the training of the acoustic echo canceller is automatically performed by using a commonly used notification sound such as a ring tone or a dial confirmation sound when a communication path is connected for incoming call or outgoing call. Will be done. For this reason, the operator does not need to perform any key operation for training, thereby reducing the operational burden on the operator.

Further, training is automatically performed every time a call is made and received, and the latest cancellation information is set in the echo canceller each time. Therefore, for example, the composition of the occupants changes and the acoustic characteristics of the space used change. However, at the start of the call, the acoustic echo canceller can be operated according to the optimal cancellation information at that time. For this reason,
The problem that the acoustic echo is transmitted to the other party at the start of the call is eliminated, so that a high quality call can always be made.

Further, even if the cancel information being set is erased due to the power interruption, the acoustic echo canceller can be operated according to the optimal cancel information at the time of starting a call. Therefore, a backup power supply for the storage element for storing the cancel information is not required, and an expensive storage element such as an EEPROM is not required, so that the circuit configuration can be simplified and inexpensive.

According to the present invention, even when the handset talk mode is selected, the talk mode is temporarily changed to the hands-free talk mode, and the initial training of the acoustic echo canceller is performed in this state. . Therefore, for example, even if the mode is switched from the handset call mode to the hands-free call mode during a call, the acoustic echo canceller has already been trained to the optimal characteristics, so howling does not occur immediately after the start of the hands-free call. This enables high quality hands-free communication. In addition, the present invention focuses on the possibility that, even when a call is started in the handset call mode, the handset may be switched to the hands-free call mode during the call thereafter, and only during the call path connection control, that is, in the handset call, Before the start, the handset communication mode is temporarily switched to the hands-free communication mode to perform the training of the echo canceller. Therefore, according to the present invention, once a call is started, no training can be performed thereafter, thereby maintaining a high-quality call without interruption of the call due to training. .

Furthermore, if the existing ring tone or dial confirmation tone is not used as it is for training but is replaced or converted into a sound containing a frequency component necessary for training and output, optimal cancellation can be achieved. Information can be obtained.

[0020]

FIG. 1 is a circuit block diagram showing the configuration of an automobile radio telephone apparatus according to an embodiment of the present invention.

In FIG. 1, a carrier signal is received by an antenna 1 via a predetermined radio communication channel, and then input to a receiving circuit (RX) 3 via a duplexer (DUP) 2. In the receiving circuit 3, the received carrier signal is combined with the local oscillation signal output from the frequency synthesizer 4 and converted into an intermediate frequency signal. Then, the received intermediate frequency signal is input to a digital demodulation circuit (DEM) 6R. In the digital demodulation circuit 6R, the received intermediate frequency signal is digitally demodulated and converted into an analog baseband signal. This baseband signal is supplied to the A / D converter 7
After being converted into a digital signal by R, error correction processing is performed by an error correction code decoding circuit (CH-COD) 8.
Subsequently, the audio code decoding circuit (SP-COD) 9 performs a decoding process. The digital reception signal output from the audio codec 9 is converted to an acoustic echo canceller (E
After passing through (C-CAN) 10, the signal is converted into an analog signal by a D / A converter 21R and then output from a speaker 22.

On the other hand, the transmitted voice signal collected by the microphone 23 is converted into a digital signal by the A / D converter 21S, and then subjected to echo cancellation processing by the acoustic echo canceller 10. Then, the transmission signal on which the echo cancellation processing has been performed is input to the voice code decoding circuit 9. The voice codec 9 encodes the digital transmission signal, and the signal is then error-correction-coded by the error-correction codec 8.
The encoded digital transmission signal is D /
After being converted into an analog signal by the A converter 7S, it is input to the digital modulation circuit (MOD) 6S. In the digital modulation circuit 6S, digital modulation of a carrier is performed using the digital transmission signal as a modulation signal. As the digital modulation method, for example, a QPSK method is used. The transmission signal output from the digital modulation circuit 6S is combined with a local oscillation signal output from the frequency synthesizer 4 by a transmission circuit (TX) 5 and converted into a signal in a radio frequency band. Transmitted from the antenna 1 via the antenna 1.

Reference numeral 24 denotes a console unit (CU), which includes a switch group such as a transmission switch and a dial key, and a display unit such as a light emitting diode or a liquid crystal display for displaying an operation state of the apparatus. Are arranged. Reference numeral 26 denotes a power supply circuit which generates a power supply voltage Vcc based on the output voltage of the car battery 25 and supplies it to each circuit.

Incidentally, the acoustic echo canceller 10
Is configured as follows. FIG. 2 is a circuit block diagram showing the configuration together with peripheral circuits. In this figure, the same parts as those in FIG. 6 are denoted by the same reference numerals. The acoustic echo canceller 10 includes an adaptive filter 11, an adder 12, and a RAM 1 for storing cancellation information.
3 and a changeover switch 14 for switching the reception signal path.

The adaptive filter 11 takes in the residual signal TS output from the adder 12 and performs an adaptive operation to reduce the residual signal TS to zero, whereby the acoustic characteristics of the used space, that is, the echo Estimate the route. And
Echo cancellation information is created from the echo path estimation result, a pseudo echo signal EES is generated based on the cancellation information and the reception signal RS, and the pseudo echo signal EES is supplied to the adder 12. Further, the cancellation information is written in the RAM 13. The adder 12 performs digital operation for subtracting the pseudo echo signal EES from the echo signal ES output from the A / D converter 21S, and outputs the residual signal TS to the speech codec 9 as a transmission signal. I do. The changeover switch 14 is formed of, for example, a semiconductor switch, performs a switching operation in accordance with the changeover control signal SS output from the control circuit 30, and selectively switches the speech codec 9 and the control circuit 30 to the D / A converter 21R. Connect to

The control circuit (CONT) 30 includes, for example, a microcomputer as a main control unit. The control circuit (CONT) 30 has, in addition to ordinary control functions such as a wireless communication channel setting control means and a call control means accompanying an outgoing / incoming call, etc. A training control unit 31 for the acoustic echo canceller 10 is provided.

The training control means 31 switches the changeover switch 14 of the acoustic echo canceller 10 to the control circuit 30 side during the output period of the ring tone and the output period of the dial confirmation sound during the control of the connection of the telephone line accompanying the outgoing call and the incoming call. In this state, RO provided in control circuit 30
The ring tone data and the dial confirmation sound data are read from M, and these data HD are supplied to the D / A converter 21R through the changeover switch 14, and the speaker 22 outputs the ring tone and the dial confirmation sound. Here, the ring tone data and the dial confirmation sound data are set in the same manner as the conventional ring tone data and the dial confirmation sound data with respect to the intermittent period and the output time, but the frequency is used for training of the acoustic echo canceller 10. The sound is set to effectively include the required frequency. Next, the operation of the device configured as described above will be described according to the control procedure of the control circuit 30.

In the standby state, the control circuit 30 of the radio telephone apparatus repeatedly monitors the arrival of incoming data and the operation of the transmission switch in steps 3a and 3b as shown in FIG.

In this state, it is assumed that incoming data arrives from a radio telephone base station (not shown). Then, if the incoming data is for the own station and the own station can accept the incoming data, control circuit 30 returns the incoming response data in step 4a as shown in FIG. And
Step 4b waits for the arrival of the radio channel designation data from the base station. When the radio channel designation data is received, control for setting the radio communication channel designated by the designation data is executed at step 4c.

When the setting of the wireless communication channel is completed, the control circuit 30 sends the acoustic echo canceller 10
Start training control. That is, the control circuit 3
0 outputs a switching control signal SS to the changeover switch 14 of the acoustic echo canceller 10 in step 4d, thereby disconnecting the reception signal path and connecting the control circuit 30 instead. Then, in step 4e, the ring tone data is read from the ROM, and
To the D / A converter 21R. Therefore, a ring tone is output from the speaker 22, thereby notifying the user that an incoming call has occurred.

At this time, a part of the ring tone is converted into an acoustic echo EC and input to the microphone 23. The echo signal ES is digitized by the A / D converter 21S and then input to the acoustic echo canceller 10. You. Then, in the acoustic echo canceller 10, training is performed based on the ringtone, and the cancellation information of the echo path estimated by the training is written in the RAM 13. When the optimum cancellation information corresponding to the echo path of the used space is stored in the RAM 13, the control circuit 30 determines that the training has been completed, and
The process shifts from step f to step 4g, where the off-hook operation is monitored. In this state, if the user responds by performing the off-hook operation, the control circuit 30 returns the changeover switch 14 to the receiving signal path side in step 4h, and then shifts to the call control.

Therefore, in the call state, the acoustic echo canceller 10 starts the operation for canceling the echo signal based on the optimal cancel information stored in the RAM 13 by the training using the ring tone. Therefore, the acoustic echo EC generated during a call is reliably canceled from the start of the call, and is not transmitted to the other party. For this reason, the speaker can make a call with good quality from the start of the call.

The acoustic echo canceller 10 performs the echo signal canceling operation while updating the cancellation information while following the change in the echo path in the used space even during a call. Therefore, even when the echo path changes due to, for example, opening of a car window or moving a seat during a call, the optimum canceling operation can be performed at any time by following the change in the echo path. .

Before the end of the training,
When the user performs the off-hook operation, the control circuit 30 immediately shifts to step 4h at that time and switches the changeover switch 1
4 is restored, and the flow shifts to the call control. Therefore, in this case, the call is started with the acoustic echo canceller 10 being insufficient. However, although the acoustic echo canceller 10 is in an inadequate state, the estimation of the echo path has progressed to some extent by the above training. Therefore, by starting the echo cancellation operation for the call based on the cancellation information obtained by this estimation, the call can be made relatively smoothly without generating a large acoustic echo as compared with the case where no training is performed. Can be started. In addition, the acoustic echo canceller 10 quickly converges to the optimum state due to the following operation during the call.

On the other hand, it is assumed that, for example, the user operates the transmission switch to make a call in the standby state. Then, the control circuit 30 first proceeds to step 5 as shown in FIG.
The transmission data is created in a and transmitted to the wireless telephone base station. Then, in step 5b, the return of the transmission response data from the base station is monitored, and when the transmission response data is received, control for setting the radio communication channel is performed in step 5c based on the radio channel designation information included in the data. Perform

When the setting of the wireless communication channel is completed, the control circuit 30 starts the training control of the acoustic echo canceller 10. That is, the changeover switch 1 of the acoustic echo canceller 10 is
A switching control signal SS is output to the control signal No. 4, whereby the receiving signal path is cut off and the control circuit 30 is connected instead. In step 5e, the input of the dial key is monitored. When the dial key is operated, dial data corresponding to the key is generated in step 5f and transmitted to the base station. At this time, the control circuit 30 determines in step 5g that the RO
Dial confirmation sound data is read from M, and this data is supplied to the D / A converter 21R via the changeover switch 14. Therefore, a dial confirmation sound is output from the speaker 22, so that the user can confirm that the dial operation has been reliably performed.

On the other hand, at this time, a part of the dial confirmation sound becomes an acoustic echo EC and is input to the microphone 23. The echo signal ES is digitized by the A / D converter 21S and then input to the acoustic echo canceller 10. Is done. Then, in the acoustic echo canceller 10, training is performed based on the dial confirmation sound, and the cancellation information of the echo path estimated by the training is written in the RAM 13. When the optimum cancellation information corresponding to the echo path of the used space is stored in the RAM 13, the control circuit 30 determines that the training has been completed and shifts from step 5h to step 5i. Return to the roadside. And if the other party responds by going off-hook in this state,
The device is in a call operation state.

Therefore, in the call state, the acoustic echo canceller 10 starts the operation for canceling the echo signal based on the optimal cancel information stored in the RAM 13 by the training using the dial confirmation sound. For this reason, the acoustic echo EC generated during a call
Is reliably canceled from the start of the call and is not transmitted to the other party. For this reason, the speaker can make a call with good quality from the start of the call.

As described above, according to the present embodiment, the training of the acoustic echo canceller 10 is automatically performed at the time of incoming call and at the time of outgoing call using the ring tone and the dial confirmation tone, respectively. For this reason, the user does not need to perform any operation for training, thereby reducing the operational burden.

Further, since the training is automatically performed for each incoming call and each outgoing call, the acoustic echo canceling operation is always performed based on the optimal cancel information at the time of a call. Therefore,
During standby, for example, even if the number of people in the vehicle changes and the acoustic characteristics of the space used change, the call can always be made with the best quality. Also, in this case, the user does not need to perform any troublesome operation for training, so that the burden on the user is reduced. Further, even when the power is turned off and the cancel information stored in the RAM 13 is erased, training is automatically performed at the time of a call, and the optimal cancel information is written into the RAM 13 at that time. It is no longer necessary to use a backup power supply for protection, thereby simplifying the circuit configuration. Also, EEPROM
Since there is no need to use expensive storage elements such as the above, the circuit can be made inexpensive.

Furthermore, according to the present embodiment, since the training is performed using the period during which the ring tone is generated and the period during which the dial confirmation sound is generated, there is no fear that the time required for connecting the communication path is unnecessarily long. .

The present invention is not limited to the above embodiment. For example, in a wireless telephone device having a hands-free call mode and a handset call mode, before starting a call, it is determined whether the handset call mode is selected or the hands-free call mode is selected,
When the call mode using the handset is selected, the call mode is changed to the hands-free call mode at least during the training period, and the notification sound is output from the speaker. Based on the notification sound, the acoustic characteristics of the acoustic echo canceller are changed. Training may be performed.

This has the following effects. That is, in general, when talking in the handset talking mode, no acoustic echo canceller is used, so training is not required. However, if the acoustic echo canceller training is omitted just because the call is in the handset call mode at the start of the call, the acoustic echo immediately after the switch is canceled when the handset call mode is switched to the hands-free call mode during a call. It is sent as it is without being received. However, as described above, even in the case of the handset call mode, if the training mode of the acoustic echo canceller is temporarily switched to the hands-free call mode before the start of the call, the acoustic echo is included even if the mode is switched during the call. A transmission signal that is not transmitted can be transmitted, so that the communication quality can be kept high.

In the above embodiment, the dial confirmation tone is used as the training signal at the time of calling, but a ringback tone may be used instead. Training may be performed using the dial confirmation sound and the ringback tone, respectively. In this way, a sufficiently long training period can be secured. Further, a voice message may be output using a voice synthesis circuit instead of the ringtone or ringback tone. In this way, it is possible to perform more accurate training than in the case of using a sound such as a ringtone or a ringback tone.

Further, in the above-described embodiment, the case where the present invention is applied to a digital radio telephone apparatus has been described as an example. However, the present invention can be applied to a so-called dual mode apparatus which performs communication by selectively using a digital mode and an analog mode. Alternatively, the present invention may be applied to a device having only the analog mode. Further, the present invention may be applied not only to a wireless telephone device but also to a wired telephone device having a hands-free call mode.

In addition, the circuit configuration of the acoustic echo canceller and the control procedure and control contents of the training control means can be variously modified without departing from the gist of the present invention.

[0047]

As described above in detail, according to the present invention, an acoustic echo canceller for canceling an acoustic echo generated when a sound output from a speaker for hands-free communication is input to a microphone, With the training means, by this training means,
By training the acoustic characteristics of the acoustic echo canceller based on the sound output from the speaker, it is possible to eliminate the operation for training at all and reduce the operational burden on the user. And even if the acoustic characteristics of the space used change or the power is turned off, the operating state of the echo canceller can always be set to the optimum state without the need for training operation or backup power supply, It is possible to provide a speech communication apparatus and a training method for an acoustic echo canceller that can improve the speech quality and simplify the circuit size.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of a wireless telephone device according to one embodiment of the present invention.

FIG. 2 is a circuit block diagram showing a main configuration of the device shown in FIG. 1;

FIG. 3 is a flowchart showing standby control procedures and control contents of a control circuit in the apparatus shown in FIG. 1;

FIG. 4 is a flowchart showing an incoming call control procedure and control contents of a control circuit in the apparatus shown in FIG. 1;

FIG. 5 is a flowchart showing a transmission control procedure and control contents of a control circuit in the apparatus shown in FIG. 1;

FIG. 6 is a circuit block diagram showing a configuration of a conventional acoustic echo canceller.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... Duplexer (DUP), 3 ... Receiving circuit (RX), 4 ... Frequency synthesizer (SYN), 5 ... Transmitting circuit (TX), 6R ... Digital demodulation circuit (DE)
M), 6S ... Digital modulation circuit (MOD), 7R, 2
1S A / D converter, 7S, 21R D / A converter, 8
... Error correction code decoding circuit (CH-COD), 9 ... Speech code decoding circuit (SP-COD), 10 ... Acoustic echo canceller (EC-CAN), 11 ... Adaptive filter, 12 ...
Adder, 13 ... RAM for storing cancellation information, 14 ...
Changeover switch, 22 ... speaker, 23 ... microphone,
24: console unit (CU), 25: battery,
26 power supply circuit, 30 control circuit (CONT), 31
Training control means, EC: acoustic echo, RS: reception signal, ES: echo signal, EES: pseudo echo signal, T
S: a transmission signal (residual signal).

Continuation of the front page (72) Inventor Koichi Ito 3-1-1 Asahigaoka, Hino-shi, Tokyo Inside the Toshiba Hino Plant (56) References JP-A-64-50655 (JP, A) JP-A-1- 135132 (JP, A) JP-A-2-224559 (JP, A) JP-A-62-16623 (JP, A) JP-A-64-24658 (JP, A) JP-A-3-20564 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B 3/00-3/44

Claims (2)

(57) [Claims] A speaker separate from a handset for loudspeaker output of a reception voice signal and a microphone for collecting a transmission sound and outputting a transmission signal, and performing a hands-free call using these speakers and the microphone. An audio echo canceller for canceling an acoustic echo generated when a sound output from the speaker is input to the microphone; and an output from the speaker during communication path connection control. based on a predetermined notification sound is, the to and a training means for training the acoustic characteristics of the acoustic echo canceller, the training means, call by the handset mode
Is selected or hands-free call mode is selected.
The call mode with the handset
If selected, set this call mode to at least
Change to hands-free call mode only during the training period
And output the notification sound from the speaker.
Based on the acoustic characteristics of the acoustic echo canceller
Voice communication device characterized in that 2. Hands provided separately from the handset
Hands- free sound output from the speaker for free calls
In a training method of an acoustic echo canceller for canceling an acoustic echo generated by being input to a microphone for a call, the acoustic echo canceller is controlled based on a predetermined notification sound output from the speaker during a communication path connection control. When training the acoustic characteristics of the
Mode is selected or hands-free call mode is selected
Call mode by handset
If you select
Change to hands-free call mode only during training
And output the notification sound from the speaker.
The acoustic characteristics of the acoustic echo canceller based on the
Acoustic echo canceller a method of training, characterized in that so as to Ningu.