JPH09326733A - Echo cancellation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cost by surely processing echo cancellation in the case of hand-free speech for a cellular telephone system or the like so as to reduce a signal processing scale and a equipment scale. SOLUTION: A received voice signal Sa from a reception section of a cellular telephone set is amplified by an amplifier 14a and a voice is outputted from a speaker 14. A voice St at the speech by a TX microphone 11 and a voice output of the received voice signal Sa from the speaker 14 are inputted by the device and its mixed voice signal Se is inputted to a differential amplifier circuit 13. A transmission signal from EC microphone 12 is amplified by an amplifier 12a and inputted to the differential amplifier circuit 13, in which the mixed voice signal Se from the TX microphone 11 and the echo voice signal through the EC microphone 12 and an amplifier 12a are amplified differentially to conduct echo cancellation processing and the transmission voice signal Sb is sent to a transmission section of the cellular telephone set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an echo canceling device for use in a hands-free call such as an automobile telephone system and for canceling an echo sound generated between a received voice and a transmitted voice during conversation.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing the structure of a conventional echo canceling apparatus. In FIG. 4, this device is used for a hands-free call such as an automobile telephone system. A voice signal received from a receiving portion of an automobile telephone is converted into a digital signal by an A / D converter 21 and a digital signal processor. It is input to the signal processing circuit 22 composed of (DSP). The signal processing circuit 22 samples the frequency characteristic and level of the received voice signal. The signal processing circuit 22 also performs echo cancellation processing and attenuator processing, and sends the received audio signal converted into an analog signal by the D / A conversion circuit 23 to the speaker 26 through a low frequency amplification circuit (not shown).

A transmission signal in conversation from the microphone 27 is amplified by a low frequency amplifier circuit (not shown) and then A /
The digital signal is converted by the D conversion circuit 24 and input to the signal processing circuit 22. The signal processing circuit 22 samples the frequency characteristics and the level of the digital transmission signal. At the same time, the frequency characteristic and level of the received voice signal are compared with the frequency characteristic and level of the transmission signal, and echo cancellation processing and attenuator processing are performed as necessary, and the transmission signal is subjected to the D / A conversion circuit 25. Output to. Here, the transmission signal of the digital signal is converted into an analog signal and sent to the transmitting unit of the car telephone. In this way, echo cancellation during a hands-free call such as a car telephone system is processed.

[0004]

However, in the echo canceling device of the above-mentioned conventional example, the signal processing circuit 2 such as a DSP for processing the echo canceling process and the attenuator.
2, A / D conversion circuits 21, 24 and D / A conversion circuit 2
3, 25 is required, and there is a drawback that the signal processing scale and the device scale are increased.

The present invention solves the problems in the prior art as described above. It becomes possible to reliably perform echo cancellation during a hands-free call in an automobile telephone system or the like, and at the same time, its signal processing scale and device scale. To provide an excellent echo canceling device that can reduce the cost and reduce the cost.

[0006]

In order to achieve the above object, the echo canceling apparatus of the present invention uses an echo sound signal from a mixed signal in which a sound transmission signal from a transmission microphone and a sound output from a speaker are mixed. Since the transmission signal from the transmission microphone that has been canceled is output as the transmission voice signal, echo cancellation is reliably performed during a hands-free call such as a car telephone system, and the signal processing scale and device scale are It is possible to reduce the cost and reduce the cost.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is such that a speaker that outputs a received voice signal as a voice, a microphone for transmitting a voice signal, and an echo voice from the speaker are input. When the echo canceling microphone that outputs the echo signal when the sound is output, the mixed signal in which the sending signal from the sending microphone and the sound output from the speaker are mixed and the echo sound signal from the echo canceling microphone are input. A differential amplifier circuit that outputs a transmission signal from a transmission microphone that cancels an echo voice signal from the mixed signal as a transmission voice signal, and when using it for a hands-free call of an automobile telephone, Echo cancellation during hands-free calling such as car telephone system is reliably performed, and the signal processing Is reduced in size and device size, it has the effect of cost reduction is possible.

Further, in the invention as set forth in claim 2, the microphone for transmission is arranged at a position where the voice during the conversation is sufficiently inputted, and the echo canceling microphone is inputted with the echo voice from the speaker. In addition, it is arranged at a position where the transmitted voice is not input.

According to a third aspect of the present invention, there is provided a band effect filter for extracting a frequency component of an echo sound signal from a transmission microphone when a sound output from a speaker is input, and the band effect filter. The switch for stopping the transmission of the echo sound signal from the echo canceling microphone in response to the above signal.

Next, an embodiment of the echo canceling apparatus of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram showing the configuration of an echo canceling apparatus according to the first embodiment. In FIG. 1, the first embodiment is a microphone for transmitting (hereinafter abbreviated as TX) 11 that transmits a speech by a car telephone and outputs a speech signal in the conversation (call).
And an echo canceling (hereinafter abbreviated as EC) microphone 1 which receives the received voice (voice output from a speaker) during conversation on a car phone and outputs an echo voice signal.
And 2. Further, an amplifier 12a that amplifies and outputs an echo sound signal from the EC microphone 12, and a transmission sound that is differentially amplified by the echo sound signal from the amplifier 12a and the sound signal from the TX microphone 11 and is subjected to echo cancellation processing. It has a differential amplifier circuit 13 using an operational amplifier or the like for transmitting the signal Sb to a transmitter of a car telephone (not shown).

Further, it has a speaker 14 for outputting the received voice signal Sa from the receiving section of the automobile telephone, and an amplifier 14a for amplifying and transmitting the received voice signal Sa from the receiving section of the automobile telephone to the speaker 14. ing. The audio output (received audio signal Sa) from the speaker 14 is input to the TX microphone 11, amplified by the amplifier 12a, and input to the differential amplifier circuit 13. In this case, the TX microphone 11 is at a position where the voice St during conversation is sufficiently input,
For example, it is placed at the mouth of the user. The EC microphone 12 is arranged so that the echo voice signal of the voice output from the speaker 14 is input and the voice St during conversation is not input. That is, the speaker 14 and the TX microphone 11 are arranged at the same distance as each other, and the directivities thereof are opposite to each other so that the voice St during conversation is not input.

Next, the operation of the first embodiment will be described. FIG. 2 is a diagram for explaining a signal processing state in the first embodiment.

In FIG. 1 and FIG. 2, the received voice signal Sa from the receiver of the automobile telephone is amplified by the amplifier 14a and output as voice from the speaker 14. In addition, the TX microphone 11 includes a voice St and a speaker 1 during a call (conversation).
The voice output (received voice signal Sa) from 4 is input,
The mixed audio signal Se is output to the differential amplifier circuit 13.
The TX microphone 11 is arranged at a position where the voice St during conversation is sufficiently input, for example, at the mouth of the user, and the TX microphone 11 includes the speaker 1
The voice output of the received voice signal Sa is input from 4, and is amplified by the amplifier 12a and output to the differential amplifier circuit 13.

The EC microphone 12 is located at the same distance between the speaker 14 and the TX microphone 11, and is arranged so that its directivity is opposite so that the voice St during conversation is not input. There is. That is, the voice output of the reception voice signal Sa is input, and the voice St during conversation is not input. In the differential amplifier circuit 13, the mixed audio signal Se from the TX microphone 11 and E
A signal through the C microphone 12 and the amplifier 12a is input, the mixed voice signal Se and the echo voice signal from the amplifier 12a are differentially amplified, echo cancellation processing is performed, and the transmission voice signal Sb is not shown in the vehicle. Send to the transmitter of the telephone.

(Second Embodiment) FIG. 3 is a block diagram showing the configuration of an echo canceling apparatus according to the second embodiment. In the first embodiment, the EC microphone 12 is arranged so that the echo voice signal of the voice output of the reception voice signal Sa is input and the voice St during conversation is not input. EC microphone 12
This corresponds to the case where the voice St at the time of conversation is input.

In FIG. 3, in the second embodiment, a bandpass filter (BPF) 17 for passing a band signal having a frequency corresponding to the received voice signal Sa is provided on the input side of the amplifier 14a in the configuration shown in FIG. ing. Furthermore, when the echo sound signal (reception sound signal Sa) of the sound output from the speaker 14 is input to the TX microphone 11, a band effect filter (pass filter) that passes the echo sound signal other than the frequency component canceled by the BPF 17 from this signal ( BEF) 15 and an analog switch 16 for turning on / off the echo sound signal from the EC microphone 12 with the signal from the BEF 15 to input or not input to the differential amplifier circuit 13.

Next, the operation of the second embodiment will be described. Received audio signal Sa from the receiver of the car phone
Specific band signal, that is, the reception frequency band (received voice signal Sa) at the time of a call is extracted by the BPF 17, and the amplifier 1
Audio is output through the speaker 4a and the speaker 14. In addition, the mixed voice signal S in which the voice St and the echo voice signal (reception voice signal Sa) during the conversation from the TX microphone 11 are mixed.
From e, the echo audio signal other than the frequency component (received audio signal Sa) extracted by the BPF 17 is extracted by the BEF 15. The analog switch 16 is turned off by this extracted signal, and the output of the echo sound signal from the EC microphone 12 to the differential amplifier circuit 13 is stopped. As a result, the echo voice signal mixed in the voice St at the time of conversation from the TX microphone 11 is input to the differential amplifier circuit 13, so that the effect of echo cancellation is reduced as compared with the first embodiment, but from the EC microphone 12. The echo sound signal of is no longer reliably input to the differential amplifier circuit 13.

[0019]

As described above, according to the present invention, the echo voice signal is canceled from the mixed signal in which the voice transmission signal and the voice output from the speaker are mixed, and the echo voice signal is output as the transmission voice signal. Echo cancellation during hands-free calls such as is reliably performed,
The signal processing scale and the device scale are reduced, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an echo canceling device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a signal processing state in the same embodiment.

FIG. 3 is a block diagram showing a configuration of an echo canceling device according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional echo canceling device.

[Explanation of symbols]

 11 Microphone for transmission 12 Echo cancellation microphone 12a Amplifier 13 Differential amplification circuit 14 Speaker 15 Band effect filter 16 Analog switch 17 Band pass filter Sa Received voice signal Sb Transmitted voice signal

Claims (3)

[Claims] 1. A speaker for outputting a received voice signal as a voice, a microphone for transmitting a voice for outputting a voice transmitting signal, and a microphone for echo canceling for outputting an echo signal when an echo voice from the speaker is input. A mixed signal in which a transmitted signal from the transmitting microphone and a voice output from the speaker are mixed and an echo voice signal from an echo canceling microphone are input, and the echo voice signal is canceled from the mixed signal. An echo canceling device comprising: a differential amplifier circuit that outputs a transmission signal from a microphone as a transmission voice signal. 2. A transmission microphone is arranged at a position where a voice during conversation is sufficiently input, and an echo cancellation microphone is input with an echo voice from a speaker and no transmission voice is input. The echo canceling device according to claim 1, wherein the echo canceling device is arranged at a position. 3. A band effect filter for extracting a frequency component of an echo sound signal from a microphone for transmission when a sound output from a speaker is input, and a microphone for echo canceling by a signal from the band effect filter. 2. A switch for stopping transmission of an echo sound signal from the device is provided.
Echo cancellation device described.