JPH09116471A - Acoustic echo cancellor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily hold the sound quality of a cell even if external environment and the like fluctuate by controlling attenuation quantity in an attenuation part based on echo cancel quantity inputted from an echo detection part. SOLUTION: An A/D converter 2 converts an input analog sound signal from a microphone 1 into digital '←'. An operation block 3 is provided with an adaptive FIR filter F generating a pseudo echo signal from a reception signal and subtracts a pseudo sound signal from input sound. An attenuator device 4 attenuates a transmission sound signal and a CODEC device 5 compresses the sound signal. A D/A converter 8 converts a digital sound signal into analog '←', and a speaker 9 outputs sound 10. An echo detection part 11 detects echo cancel quantity in the operation block 3. A control part 12 controls the attenuation quantity of the attenuator device 4 so that it conflicts with the size relation of echo cancel quantity which the echo detection part 11 detects. Thus, satisfactory cell sound quality can be obtained with such constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic echo canceller incorporated in a voice communication device in the field of communication equipment.

[0002]

2. Description of the Related Art An acoustic echo canceller device removes an echo by generating a pseudo echo signal from a received signal in an echo removing means and subtracting the pseudo echo signal from an input signal.

A conventional acoustic echo canceller will be described below. FIG. 2 is a block diagram of a conventional acoustic echo canceller. In FIG. 2, 1 is a microphone for voice input, 2 is an A / D converter for converting an analog voice signal input from the microphone 1 into a digital signal, 3
Is an adaptive FIR that generates a pseudo echo signal from a received signal
The calculation block includes a filter F and subtracts a pseudo echo signal from an input audio signal.

Reference numeral 4 is an attenuator device for attenuating a transmission voice signal, 5 is a codec device for compressing the voice signal, 6 is a line interface circuit for exchanging the voice signal with the communication line network 7, and 8 is a digital voice signal converted into an analog signal. A D / A converter, 9 is a speaker for outputting a sound, and 10 is a sound entering the microphone 1 from the speaker 9.

The operation of the conventional acoustic echo canceller configured as described above will be described below. First,
The voice signal from the other party output to the communication line network 7 is input to the codec device 5 by the line interface circuit 6, and the compressed voice signal is converted into a linear digital voice signal. The converted voice signal is branched into two, a path a and a path b, and the D / A converter 8 and the adaptive FIR
It is input to the filter F.

The signal sent to the D / A converter 8 is converted into an analog signal and output as a voice 10 from the speaker 9. A part of this voice 10 becomes an echo, which is input to the microphone 1 and is input to the A / D converter. Converted to digital at 2.

Further, a pseudo echo signal similar to the voice 10 is generated by the adaptive FIR filter F from the received voice passing through the path a. The pseudo echo signal generated by the adaptive FIR filter F is subtracted from the audio signal input from the A / D converter 2, and the result is input to the attenuator device 4 and attenuated, and the codec device 5
The data is compressed by and is output to the communication line network 7 via the line interface circuit 6.

[0008]

However, in the above structure, the echo relationship between the speaker 9 and the microphone 1 is changed by the movement of the microphone 1, and the output gain of the speaker 9 is changed.
The amount of echo cancellation deteriorated, causing deterioration of voice communication. Further, when the amount of echo in the installation environment is large, it is not possible to generate sufficient pseudo echo, and the amount of echo cancellation is deteriorated.

Therefore, an object of the present invention is to provide an acoustic echo canceller capable of maintaining good call quality.

[0010]

SUMMARY OF THE INVENTION An acoustic echo canceller of the present invention generates a pseudo echo signal from a voice signal, attenuates the pseudo echo signal generated from the voice signal, and attenuates the output of the calculation block. The output unit includes an attenuator for outputting, an echo detector for detecting the amount of echo cancellation in the calculation block, and a controller for changing the amount of attenuation in the attenuator based on the amount of cancellation input from the echo detector.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention generates a pseudo echo signal from a voice signal and subtracts a pseudo echo signal generated from the voice signal, and an output of the calculation block. An attenuation unit that attenuates and outputs, an echo detection unit that detects an echo cancellation amount in the calculation block, and a control unit that changes the attenuation amount in the attenuation unit based on the cancellation amount input from the echo detection unit. It is possible to balance the pseudo echo with the external environment and improve the call sound quality.

Further, according to the second aspect of the invention, the attenuator is controlled so as to decrease the attenuation amount when the echo cancellation amount increases and increase the attenuation amount when the echo cancellation amount decreases. An appropriate amount of attenuation can be obtained.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an acoustic echo canceller according to an embodiment of the present invention. In FIG. 1, 1 is a microphone for voice input, 2 is an A / D converter for converting an analog voice signal input from the microphone 1 into a digital signal, 3 is an adaptive FIR filter F for generating a pseudo echo signal from a received signal. It is a calculation block that is provided and subtracts the pseudo echo signal from the input audio signal.

Reference numeral 4 denotes an attenuator device as an attenuator for attenuating a transmission voice signal, 5 a codec device for compressing the voice signal, 6 a line interface circuit for exchanging the voice signal with the communication line network 7, and 8 a digital voice signal. Is an analog-to-digital converter, 9 is a speaker for outputting audio, and 10 is audio entering the microphone 1 from the speaker 9.

Reference numeral 11 denotes an echo detector for detecting the amount of echo cancellation in the arithmetic block 3, and reference numeral 12 changes the amount of attenuation of the attenuator device 4 so as to conflict with the magnitude relationship of the amount of echo cancellation detected by the echo detector 11. It is a control unit.

Next, the operation of the acoustic echo canceller of this embodiment will be described. First, the compressed voice signal from the other party input from the communication line network 7 is input to the codec device 5 via the line interface circuit 6, and this voice signal is converted into a linear digital voice signal. The converted voice signal is branched into two routes, a and b, and D
It is input to the / A converter 8 and the adaptive FIR filter F.

The signal sent to the D / A converter 8 is converted into an analog signal and output from the speaker 9 as a sound 10. A part of the voice 10 becomes an echo, is input to the microphone 1, and is converted into digital by the A / D converter 2.

Further, a pseudo echo signal similar to the voice 10 is generated by the adaptive FIR filter F from the received voice passing through the path a. Then, the pseudo echo signal generated by the adaptive FIR filter F is subtracted from the audio signal input from the A / D converter 2, and the result is input to the attenuator device 4.

Now, in the echo detection section 11, the subtracted signal d and the signal c from the A / D converter 2 delayed by the same amount as in the operation block 3 are compared and calculated to cancel the echo. Detect the amount. The detected echo cancellation amount is sent to the control unit 12. The control unit 12 controls the attenuator device 4 such that the attenuation amount increases when the echo cancellation amount is small, and the attenuation amount decreases when the echo cancellation amount is large. In this way, by detecting the amount of echo cancellation and controlling the attenuator device 4 which attenuates the transmission voice signal based on the data, the voice echo can be adaptively attenuated.

[0020]

The acoustic echo canceller of the present invention generates a pseudo echo signal from a voice signal and subtracts the pseudo echo signal generated from the voice signal.
An attenuator that attenuates and outputs the output of the operation block,
Since the echo detection unit that detects the echo cancellation amount in the calculation block and the control unit that changes the attenuation amount in the attenuation unit based on the cancellation amount input from the echo detection unit are included, the voice echo is adaptively attenuated. As a result, good call quality can be obtained even if the external environment changes.

[Brief description of the drawings]

FIG. 1 is a block diagram of an acoustic echo canceller according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional acoustic echo canceller.

[Explanation of symbols]

 3 Calculation block 11 Echo detection unit 12 Control unit

Claims (2)

[Claims] 1. A calculation block for generating a pseudo echo signal from a voice signal and subtracting the pseudo echo signal generated from the voice signal, an attenuator for attenuating and outputting the output of the calculation block, and an echo in the calculation block. An acoustic echo canceller, comprising: an echo detector that detects the amount of erasure; and a controller that changes the amount of attenuation in the attenuator based on the amount of erasure input from the echo detector. 2. The control unit controls the attenuating unit so as to decrease the attenuation amount when the echo cancellation amount increases and increase the attenuation amount when the echo cancellation amount decreases. 1. The acoustic echo canceller according to 1.