JPS6379449A - Sound echo canceller with loudspeaker function - Google Patents

Abstract

PURPOSE:To prevent a tape of an echo canceller from being corrected by a detour sound picked up by a microphone by controlling an echo canceller at a level of a reception signal from a remote end side before signal addition for loudspeaking. CONSTITUTION:At first, the sound signal Y picked up by a microphone is inputted to a subtraction circuit 93 through an amplifier 3 and an A/D conversion section 5. Then the subtraction circuit 93 subtracts an estimated echo signal Y generated by a filter 92 to output a residual signal E. Then the residual signal E is sent to a remote end through a D?A conversion section 7 and added to a signal received from the remote end by an adder circuit 11 through a variable attenuator 10. On the other hand, a sound detection section 12 detects the level of a reception signal from the remote end aud outputs a signal stopping coefficient correction to a coefficient correction section 91 when the level is below a prescribed level. Thus, the correction of the tap of the echo canceller is prevented due to the detour of a sound picked up by the microphone.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an acoustic echo canceller in a remote conference audio system), particularly an acoustic echo with a public address function that requires a public address function in a large conference room or the like. The present invention relates to a canceller device.

[Conventional technology]

In recent years, with the development of teleconference systems, acoustic echo cancellers have been used to suppress howling and echoes and to provide clear and natural remote conferences. However, it is difficult to use the echo canceller with the in-room amplification function.

As a solution to this problem, a conference call transmission/reception device has been proposed that divides the room into zones and uses multiple echo cancellers to provide amplification functions (Special PfI 1986-15).
3221).

An example of a conventional acoustic echo canceller device with amplification function is shown in FIG. 2 and will be described.

In the figure, 1 is a microphone cophone, 2 is a speaker, 3.4
is an amplifier circuit, 5 and 8 are analog-to-digital converters (A
/D ), 6.7 is the digital-to-analog converter (D/
A). 9 is an echo canceller, and this echo canceller 9 includes a coefficient correction section 91 that estimates the transfer characteristic from the speaker 2 to the microphone 1, and an input signal of the speaker 2 and the coefficient correction section 9. The filter 92 generates a signal that goes around to the microphone 1 based on the transfer function determined by the above, and the subtraction circuit 93 subtracts the output of the filter 92 from the output of the microphone 1. 10 is a variable attenuator that adjusts the level of the output signal of the subtraction circuit 93, and 11 is an adder circuit that adds the output of the variable attenuator 10 to the received signal from the far end side. Then, the digital-to-analog converter (D/A
') The output of γ is sent out to the outside as a transmission output 5OUT, and the external reception power RIM is configured to be supplied to an analog-to-digital converter (A/D) 8.

[Problems to be Solved by the Invention] In the public address system using the conventional echo canceller described above, modification of the coefficients of each tap of the filter is stopped after initial training is completed. With this method, it is impossible to follow environmental changes such as indoor temperature and humidity, so in the worst case, howling may even occur. Therefore, the second
As shown in the figure, by using an echo canceller and continuing to modify the coefficients, it is possible to stop howling and respond to environmental changes. However, in this method, the sound picked up by the microphone is routed to the reception input RIN side of the echo canceller.

When , the correlation between the echo canceller's transmission output SIN and the input signal to the receiver's input terminal R4N is very strong (they are exactly the same), so if double talk is detected incorrectly, each of the internal filters There was a problem that the coefficient of the tap changed greatly.

[Means for solving problems]

The acoustic echo canceller device with amplification function of the present invention includes a coefficient correction section that can stop estimating the transfer characteristic from the speaker to the microphone based on an external signal, and a transfer function calculated using the input signal of the speaker and the coefficient correction section. a filter that generates a signal input to the microphone, a subtraction circuit that subtracts the output of the filter from the output of the microphone, a terminal that outputs the output of the subtraction circuit to the far end, and a terminal that outputs the output of the subtraction circuit to the far end. A terminal for receiving a received signal, a voice detection unit that detects the voice level of the signal from the far end side and sends a signal to stop estimation to the coefficient correction unit when the level is below a certain level, and the level of the output signal of the subtraction circuit. and an adder circuit that adds the output of the variable attenuator to the received signal from the far end side.

[Effect]

In the present invention, the modification of the echo canceller is controlled based on the level of the received signal from the far end before signal addition for amplification.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a block diagram showing an embodiment of an acoustic eco-bag frame canceller installation with amplification function according to the present invention.

In FIG. 1, the same reference numerals as in FIG. 2 indicate corresponding parts, and 12 detects the signal from the far end side and the audio level, and when the level is below a certain level, sends a signal to the coefficient correction unit 91 to stop the estimation. This is the audio detection unit that sends the audio. The coefficient correction unit 91 is configured to be able to stop estimation of the transfer characteristic from the speaker 2 to the microphone 1 using an external signal.

It also has a terminal for outputting the output of the subtraction circuit 93 to the far end side (transmission output 5OUT terminal) and a terminal for receiving a reception signal from the far end side (reception manual RUN terminal).

Next, the operation of the embodiment shown in FIG. 1 will be explained.

First, the audio signal Y picked up by microphone 1 is sent to amplifier 3.
The signal is then input to the subtraction circuit 93 through the analog-to-digital converter ('A/D) 5. Then, this subtraction circuit 93 subtracts the estimated echo signal Y generated by the filter 92 and outputs a residual signal E.

Here, an echo canceler is generally composed of a coefficient correction section 91, a filter 92, and a subtraction circuit 93, which corrects the coefficients of each tap of the filter 92 based on the residual signal E, so that the residual signal E becomes zero. Call it 9.

Next, the residual signal E is converted to a digital-to-analog converter (D
/A) is transmitted to the far end through 7 and is input to the summing circuit 11 through the variable attenuator 10. This adder circuit 11 adds the signal received from the far end to the output of the variable attenuator 10 through an analog-to-digital converter (A/D) 8. The addition signal X obtained by this addition circuit 11 is input to a filter 92 and a digital-to-analog converter (D/A) 6. The output of this digital/analog converter (D/A) 6 is amplified by an amplifier circuit 4 and drives a speaker 2.

On the other hand, the audio detection section 12 detects the level of the received signal from the far end, and if the level is below a certain level, outputs a signal to the coefficient modification section 91 to stop coefficient modification. Generally, echo cancellers have a correction/stop function for double talk, so this will be used as is for tMj.

That is, in the configuration of the embodiment shown in FIG. 1, the coefficient of the echo canceller is corrected only when there is a signal above a certain level in the receiver's human power RIH.
It is possible to prevent the sound picked up by the microphone from being erroneously modified in relation to the signal returned by the amplification system.

〔Effect of the invention〕

As explained above, according to the present invention, an acoustic echo canceller with amplification function can be stably operated by controlling the modification of the echo canceller based on the level of the received signal from the far end before addition of the amplification signal. Because you can
The practical effect is quite dogmatic. Furthermore, since a general echo canceller configuration does not necessarily include a function to control the termination of the correction process, this is extremely effective in that there is no need to configure a special echo canceller.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an acoustic echo canceller device with a loudspeaker function according to the present invention, and FIG. 2 is a block diagram showing an example of a conventional acoustic echo canceller device with a loudspeaker function. 1 fist ◆ 11 @ Microphone - 2 hIl/Yoshihika, 9
-...Echo canceller, 91...Rosal coefficient correction unit, 92-...Filter, 93 -e...Subtraction circuit,
10・Fist・-variable attenuator, 11・φ・addition circuit, 12
...Audio detection section.

Claims (1)

[Claims] a coefficient correction unit that can stop estimating the transfer characteristic from the speaker to the microphone using an external signal; and a filter that generates a signal that goes around to the microphone from the input signal of the speaker and the transfer function determined by the coefficient correction unit. ,
a subtraction circuit that subtracts the output of the filter from the output of the microphone, a terminal that outputs the output of the subtraction circuit to the far end, a terminal that receives a received signal from the far end, and a signal from the far end. an audio detection unit that detects an audio level and sends a signal to stop estimation to the coefficient correction unit when the audio level is below a certain level, a variable attenuator that adjusts the level of the output signal of the subtraction circuit, and a reception signal from the far end side. 1. An acoustic echo canceller device with a loudspeaker function, comprising: an adder circuit that adds the output of the variable attenuator to a signal.