JPH10308814A - Voice switch for talker - Google Patents

Abstract

(57) [Summary] The present invention relates to a voice switch used in a hands-free telephone or the like, and in a telephone with frame processing, accurately suppresses acoustic echo regardless of a time lag of a transmission / reception signal. Aim. A delay unit delays a received voice signal by a predetermined time, a received voice determination unit that determines whether to suppress a received voice signal based on the received voice signal and a transmitted voice signal, and a delay unit that delays the received voice signal. A transmitting voice determining unit that determines whether or not the transmitting voice signal is suppressed based on the received receiving voice signal and the transmitting voice signal, and a receiving-side suppression that suppresses the receiving voice signal according to a determination result of the receiving voice determining unit. And a transmitting-side suppressing means for suppressing the transmitted voice signal in accordance with the result of the determination by the transmitted voice determining means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice switch used for a hands-free telephone or the like. In a hands-free talker employing a voice switch system, it is necessary to be able to accurately suppress acoustic echo.

[0002]

2. Description of the Related Art To realize a hands-free function,
It is necessary to increase the volume of the speaker and the sensitivity of the microphone. However, in this case, as shown in FIG. 5, an acoustic echo occurs in which the received voice output from the voice output unit such as a speaker circulates to a voice input unit such as a microphone. This is a phenomenon in which one's voice sounds like an echo to the other party, and is very difficult to use. There are two methods for removing the acoustic echo: (1) an echo canceller method and (2) a voice switch method.

[0003] The echo canceller system removes an acoustic echo using an adaptive signal processing technique. For example, FIG.
As shown in (1), an acoustic echo r in which the output received voice wraps around the microphone is artificially generated inside the telephone, and is subtracted from the signal input to the microphone. The generation of the pseudo echo r 'is obtained by expressing a transfer function from the speaker to the microphone by using an FIR filter. Since this transfer function changes depending on the situation around the telephone, the filter is adaptively changed so that the error between the pseudo echo r 'and the acoustic echo r is minimized.

On the other hand, in the voice switch system, as shown in FIG. 7, the power of a speaker output voice and the power of a microphone input voice are compared, and one of them is suppressed to remove an acoustic echo. In other words, while the speaker is outputting, the signal input to the microphone has a high probability of being an acoustic echo,
During this time, by suppressing the microphone input signal, transmission of an acoustic echo to the other party is prevented.

As described above, there are two methods of removing an acoustic echo which is a problem in realizing the hands-free function, an echo canceller and a voice switch. A comparison of the advantages and disadvantages of both is as shown in FIG. 8, which is a trade-off between the processing amount and the performance. To prioritize the cost, a voice switch method will be adopted. The present invention relates to this voice switch.

FIG. 9 shows a detailed conventional structure of a hands-free telephone having the voice switch. In FIG. 9, reference numeral 1 denotes a receiving unit including a demodulator for receiving an audio signal from the other party, 2 denotes a power suppressing unit that can suppress and control the power of the received signal by changing the receiving gain gain-r,
Reference numeral 3 denotes an audio output unit which includes an amplifier, a speaker, and the like, and emits a received voice (R). Reference numeral 6 denotes a voice input unit comprising a microphone or an amplifier for inputting a transmission voice (S), 7 a power suppressing unit capable of suppressing and controlling the power of a reception signal by changing a transmission gain gain-s, and 8 a transmission voice signal. Is a transmission unit including a modulator or the like for transmitting the signal to the other party.

[0007] 4 indicates whether the received voice is suppressed by the power suppression unit 2 on the receiving side based on the magnitudes of the received voice and the transmitted voice.
This is a determination unit for determining whether or not the transmitted voice is suppressed by the power suppressing unit 7 on the transmitting side. 41 is a power calculator for calculating the power of the received signal received by the receiver 1, and 42 is the current received voice state s based on the power calculated by the power calculator 41.
-s is a sound detector that detects whether there is no sound or sound, 43 is a power calculator that calculates the power of the audio signal input to the audio input unit 6, and 44 is the current power based on the power calculated by the power calculator 43. The sound detection unit 45 detects whether the transmitted voice state sr of the transmission sound is silent or non-speech. The control unit 45 controls any one of the power suppression units 2 and 7 based on the detection results of the sound detection units 42 and 44. It is a determination unit for determining whether to use

Here, the power calculators 41 and 43 calculate the power of the input voice data according to the following formula. That is, assuming that the input audio data is x _i , the output power p _i is obtained by p _i = 10 × log [Σ (x _ij x _ij )]. Here, Σ is an addition from j = 0 to J.

As shown in FIG. 10, the sound detectors 42 and 44 comprise a comparator for comparing the input power p _i with a fixed threshold value th.
_By comparing _i with the threshold th, it is determined whether the current voice state S _i is sound or no sound. Here, s _i = 0 is silence,
s _i = 1 means sound. The judgment formula is if (p _i <th) s _i = 0 if (p _i > th) s _i = 1. This is because the input power p _i is smaller than the threshold th, the speech state s _i to "0", if greater More threshold th, in which the speech state s _i to "1". As a result, it is possible to prevent erroneous determination of existence of background noise having a threshold value th or less.

[0010] The determination unit 45 receives the reception gain gain-r of the reception power suppression unit 2 and the transmission gain ga of the transmission power suppression unit 7 according to a determination logic table shown as an example in FIG.
Controlling in-s. Here, the reception gain gain-r
And the transmission gain gain-s are in the range of 0.0 ≦ gain ≦ 1.0. In the determination logic table of FIG. 11, when the transmission voice state s−s = 0 and the reception voice state s−r = 0, the transmission gain gain-s is “0.0”, and the reception gain main−r is Set to “0.0”. When the transmitted voice state s−s = 1 and the received voice state s−r = 0, the transmitted gain “gain-s” is set to “1.0” and the received gain “gain-r” is set to “0.0”. When the transmitted voice state s−s = 0 and the received voice state sr = 1, the transmitted gain “gain-s” is set to “0.0” and the received gain “gain-r” is set to “1.0”. When the transmission voice state s-s = 1 and the reception voice state sr = 1, the reception is prioritized, and the transmission gain gain-s is set to "0.
0 ", and the reception gain gain-r is set to" 1.0 ". Control.

According to the determination result of the determination section 45, the power
-The suppression units 2 and 7 are input audio data x _iFor
And output audio data x_iOutput as x_i= X_i× gain

As described above, this voice switch system suppresses one of the received voice and the transmitted voice depending on the state of the voice.
If the other is the reception voice, the speaker output is performed, and if the transmission voice is the transmission voice, the transmission is performed. If both of them have sound, various criteria can be considered, such as a case where the received voice is prioritized, and a case where the higher voice power is prioritized.

[0013]

As described above, the voice switch system compares the state of a received voice and the status of a transmitted voice, and suppresses one of them and passes the other to remove an acoustic echo. is there. This normally eliminates the acoustic echo without any problem.However, when frame processing is performed, there is a time lag between the received voice and the transmitted voice, and it is possible to completely eliminate the acoustic echo. May not be possible.

The frame processing is used, for example, when performing a speech codec processing, and is to collectively process data for a predetermined time. FIG. 12 is a diagram for explaining this frame processing, and shows the timing from when the input voice is encoded on the transmitting side to when it is decoded and output on the receiving side. In FIG. 12, on the transmission side, the transmission voice input by the voice input unit is accumulated for a certain period of time to form a frame, and this frame is subjected to the encoding process at the timing of the second frame and the transmission process at the transmission unit. And sent to the other party. On the other side, the frame is received by the receiving unit and decoded by the decoding unit, and then the frame is emitted from the audio output unit as a received voice at the timing of the third frame. As can be seen from FIG. 12, the input voice on the transmitting side is output on the other side with a delay of at least two frames.

When this frame processing is performed by a voice switch, as shown in FIG. 13, the received voice and the transmitted voice to be compared at the time of the determination by the determination unit are the received voice and the transmitted voice which are simultaneously output from the microphone when output from the speaker. It will no longer be voice and transmitted voice. In other words, considering the time of determination as a reference, the transmitted voice input by the microphone one frame before is compared with the received voice output by the speaker after one frame. Because of this shift, it is impossible to determine whether the transmitted voice input from the voice input unit is an acoustic echo wrapping around from the voice output unit, when compared simply.

Hereinafter, this will be described in detail with reference to FIG. FIG. 13 shows the time in units of frames in the horizontal axis direction. Hereinafter, a description will be given according to the time in the frame unit.

First frame: The received data received by the receiving unit on the receiving side is voiced, and the input data input by the voice input unit on the transmitting side is voiced. Second frame: The voice on the receiving side and the voice on the transmitting side are compared by the determination unit. Since both are sound, give priority to receiving,
It is determined that the sound on the transmitting side is suppressed. Third frame: In accordance with the above determination, the output unit outputs the above-mentioned sound as "voice", and suppresses the voice on the transmitting side to "silence" before transmission. At this time, it is assumed that since the other party has interrupted the conversation, the receiving voice is interrupted, and the data received by the receiving unit becomes silent. At this point, sound was observed in the voice input unit. However, it is not known whether this sound is a conversation of the local transmitter or an acoustic echo of a sound 'that wrapped around from the audio output unit. Fourth frame: The determination unit compares the silence on the receiving side with the voice on the transmitting side, and as a result, determines that the voice on the transmitting side is not suppressed. Fifth frame: In accordance with the above determination, the receiving end outputs silence from the audio output section as silence, and the transmitting end transmits speech from the audio input section as speech without suppression.

In the above-mentioned sequence, the voiced sound is transmitted to the other party in the fifth frame. This voiced voice may be the conversation voice of the local station sender or may be transmitted from the voice output unit. I don't know if it was an acoustic echo of the sound. For this reason, in the case of the latter, the acoustic echo that had to be suppressed originally is transmitted to the other party, and the other party hears the echo of their own voice when talking is interrupted That makes this feel uncomfortable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to appropriately suppress acoustic echo in a communication device with frame processing regardless of a time lag of a transmission / reception signal.

[0020]

FIG. 1 is an explanatory view of the principle according to the present invention. In order to solve the above-described problems, the voice switch of the telephone according to the present invention includes a delay unit that delays a received voice signal received by a predetermined time, and a delay unit that receives the received voice signal and the input voice signal. Receiving voice determining means for determining whether or not to suppress the received voice signal based on the received voice signal delayed by the delay means, and whether or not to suppress the transmitted voice signal based on the input transmitted voice signal Transmitted voice determining means for determining the received voice signal, receiving side suppressing means for suppressing the received voice signal in accordance with the determination result of the received voice determining means, and suppressing the transmitted voice signal in accordance with the determination result of the transmitted voice determining means Transmitting side suppressing means. In a telephone to which this voice switch is applied, voice data is processed in block units by frame processing, and the predetermined time to be delayed by the delay means is a time lag between a received voice signal and a transmitted voice signal caused by the frame processing. Is compensated for, and the time for synchronizing the two is taken. This delay means can be constituted by a storage means for temporarily storing. In this voice switch, when determining whether to suppress the received voice signal, the received voice is compared with the input transmitted voice. When determining whether to suppress the transmitted voice signal, the currently input transmitted voice is compared with the already-received received voice observed by the speaker at the same time as the transmitted voice, and the time lag is determined. After the correction, the synchronization between the received voice signal and the transmitted voice signal is taken at the time of determination. This is realized by delaying the received voice signal by delay means such as temporary storage means.

The above voice switch has transmitted voice estimating means for estimating the state of the transmitted voice signal synchronized with the received voice signal, and receives the transmitted voice signal from the transmitted voice estimating means to receive voice determining means. To be input as a transmission voice signal.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a hands-free telephone having a voice switch according to an embodiment of the present invention. In the figure, a receiving unit 1, power suppressing units 2, 7, an audio output unit 3, an audio input unit 6, and a transmitting unit 8 are the same as the circuit elements described in the conventional device of FIG. Description is omitted.

Further, the apparatus of this embodiment has a decoding unit 9 for decoding received data and an encoding unit 10 for encoding transmitted data. For example, when a call is made by connecting personal computers, it is conceivable that the transmission capacity of the communication path is small, so that it is necessary to perform encoding. For this reason, the apparatus of this embodiment has a configuration of a hands-free function using a voice switch and a voice codec.

Further, the apparatus of this embodiment has a received voice temporary storage section 48, and the received voice from the power suppressing section 2 is delayed by a predetermined frame time. This delay time is set to a length that corrects the time difference between the transmitted voice and the received voice and synchronizes the two. In this embodiment, it is assumed that the received voice data of one frame is delayed by two frames.

In the present embodiment, instead of the determination unit 4 in the conventional apparatus, the received voice determination unit 46 and the transmitted voice determination unit 47 are used.
It has two. The received voice determination unit 46 determines whether or not the received power is suppressed by the power suppressing unit 2 on the receiving side. The received voice output from the decoding unit 9 is input as the received voice. The transmitted voice determination unit 47 determines whether or not the transmitted voice is suppressed by the power suppressing unit 7 on the transmitting side. The received voice temporary storage unit 48 is used as the received voice.
Are delayed by a predetermined frame time from the input. Since the received voice determination unit 46 and the transmitted voice determination unit 47 have the same configuration as the determination unit 4 described in the related art, a detailed description of the configuration will be omitted.

The operation sequence of this embodiment will be described with reference to FIG. FIG. 3 shows time in units of frames in the horizontal axis direction. Hereinafter, a description will be given according to the time in the frame unit.

First frame: The received data received by the receiving unit 1 on the receiving side is voiced, and the input data input by the input input unit 6 on the transmitting side is voiced.

Second frame: The received voice determination unit 46 compares the voice on the receiving side with the voice on the transmitting side. Since both voices are voiced, it is determined that the reception is prioritized, and the voice output unit 3 outputs the voice as 'voice' without suppressing the voice on the receiving side.

Third frame: In accordance with the above determination, the sound output unit 3 outputs the above sound as sound 'without being suppressed by the power suppression unit. At this time, it is assumed that since the other party has interrupted the conversation, the receiving voice is interrupted, and the data received by the receiving unit 1 is silent. At this point, the voice input unit 6
A sound is observed in. However, it is not yet known whether this sound is a conversation of the transmitter of the local station or an acoustic echo of the sound of the received voice wrapped around from the voice output unit 3.

Fourth frame: In the received voice determination section 46,
The silent on the receiving side is compared with the sound on the transmitting side, and it is determined that the silent on the receiving side is suppressed and output from the voice output unit 3 as 'silence'. Further, the transmission sound determination unit 46 compares the sound on the reception side which has been delayed by two frames in the reception sound temporary storage unit 48 with the sound on the transmission side, and determines the transmission sound according to the reception priority rule. It is determined that the power is suppressed by the power suppression unit 7 on the transmitting side and transmitted as 'silence'.

Fifth frame: According to the above determination, the receiving end outputs silence from the voice output section as silence, and the transmitting end suppresses the sound from the input section 6 and transmits it as silence.

In the above sequence, at the fifth frame,
The sound is transmitted as 'silence'. In this case, the sound input to the audio input unit 6 is synchronized with the audio output unit 3 at the same time.
Since the sound is output from the sound, there is a high possibility that the sound is an acoustic echo of the sound. However, the conventional device could not make that determination. On the other hand, according to the present embodiment, the transmission voice determination unit 47 sets the reception voice temporary storage unit 4
8 and the voice input to the voice input unit 6 is compared, so that the time lag between the voice on the receiving side and the voice on the transmitting side is calculated. If both are sound, it can be determined that the sound on the transmitting side is likely to be an acoustic echo wrapped around the sound 'output on the receiving side. It is determined that a sound is suppressed and silence is transmitted. Thereby, an acoustic echo can be removed.

FIG. 4 shows another embodiment of the present invention.
As in the above-described embodiment, the present embodiment deals with the frame delay. And a transmission voice estimation unit 49 for estimating the voice state of the transmission voice observed by the microphone of the voice input unit 6 when the reception voice is output. For the estimation of the transmitted voice, a method of averaging the power of transmitted voices in the past several frames can be used. Since the voice fluctuates relatively smoothly over time, the estimation accuracy is considered to be relatively high.

[0034]

As described above, according to the present invention,
It is possible to correct the time lag between the received voice and the transmitted voice at the time of determination, which is a problem of the voice switch using frame processing. As a result, it is possible to ensure quick removal of acoustic echoes and changes in received and transmitted voices, and to provide a more natural call.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the principle according to the present invention.

FIG. 2 is a diagram illustrating a hands-free telephone having a voice switch according to an embodiment of the present invention;

FIG. 3 is a diagram illustrating an operation sequence of the apparatus according to the embodiment.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a diagram illustrating an acoustic echo in a hands-free communication device or the like.

FIG. 6 is a diagram illustrating an echo canceller method.

FIG. 7 is a diagram illustrating an audio switch system.

FIG. 8 is a diagram comparing an echo canceller system and a voice switch system.

FIG. 9 is a diagram showing a conventional hands-free telephone having a voice switch.

FIG. 10 is a diagram illustrating a configuration of a sound detection unit in a conventional device.

FIG. 11 is a diagram showing an example of a sound / silence determination table.

FIG. 12 is a diagram illustrating a delay due to frame processing.

FIG. 13 is a diagram showing an operation sequence of the conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Receiving part 2, 7 Power suppression part 3 Audio output part 4 Judgment part 6 Audio input part 8 Transmission part 41, 43 Power calculation part 42, 44 Sound detection part 45 Judgment part 46 Reception sound judgment part 47 Speech sound judgment part 48 Received voice temporary storage unit 49 Transmitted voice estimation unit

Continuation of the front page (72) Inventor Hitoshi Matsuzawa 4-1-1 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Masato Ito 4-1-1, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited

Claims (2)

[Claims] 1. A delay means for delaying a received voice signal received for a predetermined time, and a received voice determination for determining whether or not the received voice signal is suppressed based on the received voice signal and an input transmitted voice signal. Means, transmitted voice determination means for determining whether to suppress a transmitted voice signal based on the received voice signal delayed by the delay means and the input transmitted voice signal, and the received voice determination means A speech switch for a communication device, comprising: a receiving-side suppressing unit that suppresses the received voice signal according to the result of the determination; and a transmitting-side suppressing unit that suppresses the transmitted voice signal according to the determination result of the transmitted voice determining unit. 2. The apparatus according to claim 1, further comprising: a transmitting voice estimating means for estimating a voice state of the transmitting voice signal synchronized with the receiving voice signal, and transmitting the transmitting voice signal from the transmitting voice estimating means to the receiving voice determining means. 2. The voice switch for a telephone according to claim 1, wherein the voice switch is configured to be input as a voice signal.