JPH05313673A - Acoustic system echo canceler - Google Patents

Abstract

PURPOSE:To shorten the generation time of a training noise when an initial echo path is estimated. CONSTITUTION:A noise having a certain period tau is generated by a noise generating circuit 40 and supplied to a received input signal Rin by a switching circuit 70. A switching circuit 80 outputs the noise to a received output signal Rout (speaker) repeatedly for a certain time. A transmitted input signal Sin as a current echo is stored by a switching circuit 60 and a storage circuit 50 at certain timing for a time tau. After the signal is stored, the received output signal Rout is disconnected by the switching circuit 80 and the output of the storage circuit 50 is inputted to a subtracting circuit 20 by the switching circuit 60.

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 for eliminating the wraparound (room echo) from a speaker to a microphone in a voice conference, and more particularly to an acoustic echo canceller which requires training by noise when estimating an initial echo path. Regarding

[0002]

2. Description of the Related Art A conventional acoustic echo canceller will be described with reference to FIG.

Acoustic echo cancellers perform training to estimate room echoes before normal operation.

White noise is used as a sound source used for training. Generate noise for a few seconds, make a sufficient estimation, and then start normal operation.

The timer circuit 30 outputs a switching circuit control signal for several seconds in response to a start control signal. As a result, the switching circuit 70 outputs the input from the noise generating circuit 40.
Therefore, noise is generated from the reception output signal Rout (speaker) for several seconds. After that, the switching circuit 70 outputs the reception input signal Rin to start the normal operation.

[0006]

In the above-mentioned conventional acoustic echo canceller, training by noise is performed to estimate the room echo before the normal operation, but the training noise output time is long (for example, 10 seconds). ,
There was a problem that the noise had to be heard for a long time each time it was used.

It is an object of the present invention to provide an acoustic echo canceller capable of shortening the training noise generation time.

[0008]

According to the present invention, an estimation circuit for estimating an echo in which a reception output signal wraps around a transmission input signal with reference to the reception input signal and the transmission output signal, and an estimated echo from the transmission input signal. A subtraction circuit that subtracts to obtain a transmission output signal, a timer circuit that can be controlled independently by 5 points and that starts with a start control signal, a noise generation circuit that generates noise of a specific pattern by the output 3 of the timer circuit, and a noise generation circuit Of the output and the received input signal of the timer circuit
A first switching circuit that switches according to the output of the memory circuit, and a storage circuit that can be input / output controlled by the fourth output of the timer circuit,
Received by the second output of the timer circuit, the second switching circuit which connects and selects two points from the input of the transmission signal, the input / output of the storage circuit and the output to the echo canceller, and the fifth output 5 of the timer circuit. And a third switching circuit for switching whether to output the input signal to the reception output signal.

Further, according to the present invention, it is preferable that the echo is estimated by an adaptive FIR filter with reference to a received input signal and a transmitted output signal.

[0010]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an acoustic echo canceller of the present invention, and FIG. 2 is a sequence diagram of a timer circuit.

In FIG. 1, a noise generating circuit 40 generates a noise of a specific pattern by the output 3 of the timer circuit 30 started by a start control signal, and a switching circuit 70.
Switches between the output of the noise generating circuit 40 and the reception input signal Rin by the output 1 of the timer circuit 30, and the switching circuit 80
Is the received input signal Rin due to the output 5 of the timer circuit 30.
Is output to the reception output signal terminal.

The estimation circuit 10 receives the received output signal Rout.
The echo that the (speaker) wraps around to the reception input signal Sin (microphone) refers to the transmission output signal Sout (ε) and the reception input signal Rin output from the switching circuit 70, and an adaptive FIR (finite impulse resp).
onse) type filter, and the subtraction circuit 20 subtracts the estimated echo estimated by the subtraction circuit from the transmission input signal Sin to obtain the transmission output signal Sout.

Further, the storage circuit 50 is input / output controlled by the output 5 of the timer circuit 30, and the switching circuit 60 is sent to the transmission input signal Sin and the input / output of the storage circuit 50 and the subtraction circuit 20 by the output 2 of the timer circuit 30. Select 2 points from 3 points of the output of and connect.

Next, the operation of this embodiment will be described.

In the present embodiment, the designation circuit 10 refers to the reception input signal Rin and the transmission output signal Sout (ε) to estimate the echo path, and the subtraction circuit 20.
In, the estimated echo is subtracted from the transmission input signal Sin to realize echo cancellation. Therefore, the signals required for echo path estimation are the reception input signal Rin and the transmission input signal Sin.

By the way, in the echo canceller which uses the learning identification method as the algorithm of the estimation circuit, it is known that the echo path can be estimated even by repeating the sample data in which the reception input signal Rin and the transmission input signal Sin are captured once. Has been.

Therefore, the noise generation circuit 40 generates noise having a certain repetitive pattern (cycle τ), and the switching circuit 70 gives it by the received input signal Rin. The switching circuit 80 outputs noise for a certain period of time to the reception output signal Rout (speaker). The transmission input signal Sin, which is an echo at that time, is transferred to the switching circuit 60 and the storage circuit 50.
Then, τ time is stored at a certain timing (sampling for one cycle of the noise pattern). After the storage, the reception output signal Rout is cut off by the switching circuit 80, and the switching circuit 60
The output of the memory circuit 50 is input to the subtraction circuit. At this time, the output of the memory circuit 50 repeats the data for the time τ and is synchronized with the noise generating circuit 40.

Therefore, the estimation of the initial echo path is performed by the reception input signal Rin which is the output from the noise generating circuit 40 and the transmission input signal Sin which is the output from the storage circuit 50. Therefore, according to the present invention, the noise generation time from the speaker is at least τ time.

[0020]

As described above, according to the present invention, the indoor echo due to the training noise is sampled, and the initial estimation is performed by repeatedly using the sample data. .16 sec (1280t
It has an effect that it can be shortened to ap / 8k sampling).

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a sequence diagram of a timer circuit.

FIG. 3 is a block diagram showing an example of a conventional technique.

[Explanation of symbols]

 1 to 5 output of timer circuit 10 estimation circuit 20 subtraction circuit 30 timer circuit 40 noise generation circuit 50 storage circuit 60, 70, 80 switching circuit Sin transmission input signal Sout transmission output signal Rin reception input signal Rout reception output signal

Claims (2)

[Claims] 1. An estimation circuit for estimating an echo, in which a reception output signal wraps around a transmission input signal, with reference to the reception input signal and the transmission output signal, and a transmission output signal obtained by subtracting the estimated echo from the transmission input signal. A subtraction circuit, a timer circuit capable of independent control of 5 points that starts with a start control signal, a noise generation circuit that generates a noise of a certain pattern by the output 3 of the timer circuit, an output of the noise generation circuit, and a reception input signal A first switching circuit that switches by the first output of the timer circuit, a storage circuit that can be input / output controlled by the fourth output of the timer circuit, and a transmission input signal and input / output of the storage circuit by the second output of the timer circuit. And a second switching circuit for connecting and selecting two points from the three points of the output to the echo canceller, and the fifth output 5 of the timer circuit to receive the received input signal. And a third switching circuit for switching whether to output the signal to the audio signal. 2. The acoustic echo canceller according to claim 1, wherein the echo is estimated by an adaptive FIR type filter with reference to a received input signal and a transmitted output signal.