JPH0322631A - Echo canceller - Google Patents

Abstract

PURPOSE:To easily eliminate echo by generating a pseudo echo signal for each combination of plural speakers and microphones, taking a difference between the generated pseudo echo signal and a transmission signal to off set echos with each other. CONSTITUTION:A reception signal of left and right channels from a remote equipment is branched in the inside of an echo canceller 9, the left channel is inputted to pseudo echo generating circuits 611, 612 and the right channel is inputted to pseudo echo generating circuits 621, 622. The pseudo echo generating circuit 621 generates a pseudo echo signal corresponding to an echo (broken lines E21) detoured from a speaker 22 to a microphone 31 based on the stored acoustic characteristic, and inputted to one input terminal of a subtraction circuit 721. The pseudo echo generating circuit 611 similarly generates a pseudo echo signal corresponding to an echo (broken lines E11) bypassed from a speaker 21 to a microphone 31 in response to the input of the left channel reception signal.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an echo canceller device for canceling echoes that have passed from a speaker to a microphone in a conference communication system or the like that connects a plurality of conference halls.

[Conventional technology]

Figure a is, for example, "NEC Technical Report" Vol. 37, No. 3, No. 1.
It is a block diagram showing the conventional echo canceller device shown on pages 6-20. In the figure, 1 is an amplifier that amplifies the received signal, and 2 is a speaker that is placed in the conference hall and outputs the received signal amplified by the amplifier 1 as a loudspeaker. Reference numeral 3 designates a microphone which is similarly placed in the conference hall and receives a transmission signal, and 4 designates an amplifier which amplifies the transmission signal from the microphone 3. Reference numeral 5 designates an echo canceller device arranged between these amplifiers 1 and 4 and far-end equipment in another conference hall (not shown). Reference numeral 6 denotes a pseudo-echo generation circuit provided within the echo canceller device 5, which generates a pseudo-echo signal corresponding to the acoustic coupling between the speaker 2 and the microphone 3. 7 is similarly provided in the echo canceller device 5, and inputs the transmission signal from the microphone 3 amplified by the amplifier 4 and the pseudo echo signal generated by the pseudo echo generation circuit 6, and subtracts the difference between the two. It is a circuit. Next, the operation will be explained. A reception signal sent from far-end equipment installed in another conference hall passes through the echo canceller device 5 and is input to the amplifier l. Amplifier l amplifies the received signal and sends it to speaker 2.
As shown by the broken line A, the received reception signal is amplified and output into the conference hall. In addition, the transmission signal from the conference hall is
As shown by the broken line B, the signal is input to the microphone 3 and sent to the amplifier 4. At this time, a part of the received signal output from the speaker 2 into the conference hall also enters the microphone 3 as shown by the broken line E, and is sent as an echo to the amplifier 4 together with the transmitted signal. The amplifier 4 amplifies the transmission signal on which the echo is superimposed and sends it to the echo canceller device 5. On the other hand, the reception signal from the far-end equipment is branched within the echo canceller device 5 and is also input to the pseudo echo generation circuit 6 thereof. Here, the second pseudo echo generation circuit 6 stores in advance the acoustic characteristics from the input terminal of the amplifier 1 to the output terminal of the amplifier 4, including the acoustic coupling between the speaker 2 and the microphone 3 in the conference hall. There is. Therefore, when the received signal is input to the input terminal of the pseudo echo generation circuit 6, a pseudo echo signal corresponding to the echo that has passed from the speaker 2 to the microphone 3 is generated based on the stored acoustic characteristics. is generated and inputted to one input terminal of the subtraction circuit 7. The other input terminal of the subtraction circuit 7 receives the transmission signal on which the echo from the amplifier 4 is superimposed. The subtraction circuit 7 takes the difference between the signals input to both input terminals and outputs the difference, and from its output terminal, a transmitting signal in which the superimposed echo is canceled by the pseudo echo signal is output. In this way, from speaker 2 to microphone 3
The transmitting signal from which the echo signal that has gone around is removed is sent to the far-end equipment. It will be done. In addition, when performing conference communication with two or more conference halls, the transmitting signals from the conference halls of the other parties are mixed by a mixer and input to the echo canceller device. Figure 4 shows #l conference hall and #
It is a block diagram showing an example of application to two conference halls for two venues. In the figure, 8 is a mixer that mixes the received signal from conference hall #1 and the received signal from conference hall #2. The mixed output of the .xi. Thereafter, the echo canceller device 5 operates in the same manner as shown in FIG. 3, and sends out a transmission signal in which the reflected echoes have been canceled to conference hall #1 and conference hall #2.

[Problem to be solved by the invention]

Since conventional echo canceller devices are configured as described above, they are basically for monaural sound and are difficult to apply to stereophonic sound systems.When used in conference communication systems, Localization information of the sound source cannot be obtained,
It is difficult to conduct conference communication with a sense of presence because the speaker's location etc. are unknown, and furthermore, when applied to conference communication between two or more locations, it is difficult to acoustically identify which conference venue the speaker is speaking from. There were problems such as the inability to distinguish between the two. The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain an echo canceller device that is effective when applied to conference communications using stereophonic sound, conference communications between multiple destinations, and the like.

[Means to solve the problem]

The echo canceller device according to the present invention corresponds to each of a plurality of combinations of speakers and microphones.
A pseudo-echo generation circuit that generates a pseudo-echo signal according to the acoustic coupling of the combination of the speaker and the microphone, and a subtraction circuit that takes the difference between the transmission signal from the microphone and the pseudo-echo signal generated by each pseudo-echo generation circuit. This is what we have set up.

[For use]

Is each pseudo echo generation circuit in this invention a combination of an associated speaker and microphone? When a received signal is input, a pseudo-echo signal corresponding to the echo that has passed from the corresponding speaker to the microphone is generated and supplied to the subtraction circuit. By canceling out the echoes, the echo signals coming from a plurality of speakers are removed, thereby realizing an effective echo canceller device that can be applied to conference communication using stereophonic sound or conference communication between multiple destinations.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing an embodiment in which the present invention is applied to a conference communication system using stereophonic sound. In Fig. 1, h is an amplifier that amplifies the received signal of the left channel, h is an amplifier that amplifies the received signal of the right channel, and 2I is a conference that amplifies the received signal of the left channel amplified by the amplifier h. Speakers in the hall, ・2■ are amplifiers
This is a speaker in a conference hall that amplifies and outputs the right channel reception signal amplified by g. Is 3I a meeting? 3t is a microphone placed in the conference room and receives the left channel transmission signal manually; 3t is a microphone also placed in the conference hall and receives the right channel transmission signal; 41 is the microphone input from microphone 3; 4■ is microphone 3! This is an amplifier that amplifies the right channel transmission signal input from the In addition, 6■1 is a pseudo echo generation circuit that generates a pseudo echo signal corresponding to the acoustic coupling between the speaker 2t and the microphone 3l, and 6■ is the speaker 2I and the microphone 3l.
6■ is a pseudo echo generation circuit that generates a pseudo echo signal corresponding to the acoustic coupling between the speaker 2 and the microphone 3■. Circuit, G2■ is speaker 2
This is a pseudo-echo generation circuit that generates a pseudo-echo signal corresponding to the acoustic coupling between (2) and the microphone 3t. 7■
is the difference between the output signal of the amplifier 4l and the pseudo echo signal generated by the pseudo echo generation circuit 6■? Subtraction circuit, 7.1
is the output signal of the subtraction circuit 7■1 and the pseudo echo generation circuit 6■
The seventh circuit is a subtraction circuit that takes the difference between the pseudo echo signal generated by the amplifier 4■ and the pseudo echo generation circuit 6I! a subtraction circuit for calculating the difference between the generated pseudo echo signal and the generated pseudo echo signal; are the output signal of the subtraction circuit Lx and the pseudo echo generation circuit 6. This is a subtraction circuit that takes the difference between 9 indicates these pseudo echo generation circuits 6■. 6+z+6zt and 6■2, and the subtraction circuit 7++. 7■, 7■ and 7t
! This is an echo canceller device consisting of: Next, the operation will be explained. Received signals from far-end equipment installed in other conference halls pass through the echo canceller device 9, and the left channel is input to the amplifier h, and the right channel is input to the amplifier l2. The amplifier 11 amplifies the manually input left channel reception signal and sends it to the speaker 2l.
The speaker 21 amplifies and outputs it into the conference hall, as shown by the broken line A1. Similarly, the amplifier l2 amplifies the input right channel reception signal and converts it into a speaker signal. power 2
t, and speaker 2■ amplifies and outputs it into the conference hall, as shown by faAz. In addition, the transmission signal from the conference hall is input to the microphone 3l for the left channel and sent to the amplifier 4, as shown by the broken line BI, and for the right channel, it is manually input to the microphone 3■ as shown by the broken line B2. Amplifier 4! sent to. At this time, a part of the received signal of the left channel, which is amplified and output from the speaker 21 into the conference hall, is shown by the broken line E. and El!
As shown in , it wraps around to microphones 3I and 33
Similarly, a portion of the right channel reception signal amplified and outputted from the speaker 2z goes around to the microphones 3l and 3■ as shown by broken lines E■ and Ezz. These are superimposed as echoes on the left channel or right channel transmission signal, respectively, and are sent to the amplifier 4I or 4I.
sent to. Amplifier 4■4. In this way, the left channel or right channel transmission signal on which the echo is superimposed is amplified and sent to the echo canceller device 9. ? On the other hand, the left channel and right channel reception signals from the far-end equipment are branched inside the echo canceller device 9, and the left channel is sent to the pseudo echo generation circuits 6■ and 6I! The right channel has pseudo echo generation circuits 6 and 6. is also entered. Here, this pseudo echo generation circuit 6■ is connected to the speakers 2. The acoustic characteristics from the input terminal of the amplifier 1■ to the output terminal of the amplifier 41, including the acoustic coupling between the microphone 31 and the microphone 31, are as follows.
The acoustic characteristics from the input terminal of the amplifier h to the output terminal of the amplifier 4, including the acoustic coupling between the speaker 2 and the microphone 31, are stored in advance in the pseudo echo generation circuit 6. Similarly, the pseudo echo generation circuit 6+z has a speaker 2, a microphone 3! including acoustic coupling with
The acoustic characteristics from the input terminal of amplifier h to the output terminal of amplifier 4■ are the same as those of speaker 2!
and microphone 3. The acoustic characteristics from the input terminal of the amplifier 1t to the output terminal of the amplifier 4o, including the acoustic coupling with the amplifier 1t, are stored. ? When the right channel reception signal is input to the input terminal, the echo-echo generation circuit 6■1 outputs the signal to the speaker 2! based on the memorized acoustic characteristics. A pseudo-echo signal corresponding to the echo (broken line Ext) that has looped around from the microphone 3I to the microphone 3I is generated and inputted to one manual terminal of the subtraction circuit 71. The output signal of the amplifier 4 is input to the other human input terminal of the subtracting circuit 7I, and the subtracting circuit 7C takes the difference between these two signals and outputs the difference. Similarly, the pseudo-echo generation circuit 6■ responds to the input of the reception signal of the left channel and generates an echo that wraps around from the speaker 2I to the microphone 3L (broken line E).
++) is generated. The subtraction circuit 7■ takes the difference between this pseudo echo signal and the output signal of the subtraction circuit 7■, cancels out each echo that has passed from the speakers 2I and 2■ to the microphone 3, and converts the left channel transmission signal into Output only. Similarly, the pseudo echo generation circuits 6 and 2 respond to the left channel reception signal, and the microphone 3t is output from the speaker 21.
The echo that went around (broken line E+■)? A corresponding pseudo echo signal is generated based on the stored acoustic characteristics and outputted to the subtraction circuit 7■. On the other hand, the subtraction circuit 7. The output signal of the amplifier 4. is also input to the subtracting circuit 7. t takes the difference between these two signals and outputs it. Also, a pseudo echo generation circuit 6. When the reception signal of the left channel is input manually, the speaker 2! A pseudo echo signal corresponding to the echo (dotted line Ext>) which has looped around from to the microphone 31 is output to the subtraction circuit 7.The subtraction circuit 7. calculates the difference between the pseudo echo signal and the output signal of the subtraction circuit 7■. Outputs a right channel transmission signal in which echoes from the speakers 2 and 2 to the microphones 3t are canceled out.In this way, each echo from the speakers 2 and 2t to the microphones 3I and 3 is canceled out. The transmission signals of the left and right channels, from which the effects of echo have been removed, are sent to the far-end equipment.As a result, the reception signals of the left and right channels without echo are exchanged between each conference room. will enable conference communication using stereophonic sound.?
In the above embodiment, the present invention is applied to a conference communication system using stereophonic sound, but it may also be applied to a conference communication system with multiple destinations. FIG. 2 is a block diagram illustrating such an embodiment. In the figure, l1 and lg are amplifiers that amplify the received signals from conference hall #1 or conference hall #2, and 21 and 2■ are speakers that amplify the received signals amplified by amplifier h or 1■ into the conference hall. It is. Reference numeral 3 denotes a microphone disposed in the conference hall, into which transmission signals to the conference halls #1 and #2 are input, and 4 an amplifier that amplifies the transmission signals input from the microphone 3. 6I is speech power 2,
6■ is a pseudo echo generation circuit that generates a pseudo echo signal corresponding to the acoustic coupling between the speaker 2■ and the microphone 3; This is an echo generation circuit. 7. is the output signal of the amplifier 4 and the pseudo echo generation circuit 6
I and 6! This is a subtraction circuit that calculates the difference between each of the generated pseudo echo signals. 10 are these pseudo? code generation circuits 61 and 6■ and subtraction circuit III7. This is an echo canceller device configured by Next, the operation will be explained. The received signal from the far-end equipment located in the conference hall #1 passes through the echo canceller device 10 and is sent to the amplifier 1. and is amplified and sent to speaker 2.
1, the sound is amplified into the conference hall as shown by the broken line A1. Similarly, the received signal from the conference hall #2 is also amplified by the amplifier 1-2 and is amplified and output from the speaker 2-2 into the conference hall as indicated by the broken line A2. Further, as shown by a broken line B, a transmission signal from the conference hall is input to the microphone 3, sent to the amplifier 4, and amplified. At this time, speaker 2
A part of each reception signal outputted into the conference hall from 1 and 2■ goes around to the microphone 3 as shown by broken lines E+ and E2, is amplified together with the transmission signal by an amplifier 4, and is sent to the echo canceller device 10. It will be done. On the other hand, the reception signals from the conference halls #l and #2 are as follows:
Branched out and inside the echo canceller device 10? It is also input to the pseudo echo generation circuit 6l or 62. The pseudo-echo generation circuits 6 and 6■ respond to the input of the reception signal and generate the loudspeaker 2 based on the acoustic characteristics stored in each.
, or a pseudo echo signal corresponding to the echo that has looped back from 2x to the microphone 3, respectively. These pseudo echo signals are sent to a subtraction circuit 7. By taking the difference between the transmission signal inputted to the amplifier 4 and the transmission signal on which the echo from the amplifier 4 is superimposed, a transmission signal with the echo canceled out is output. The transmitted signal from which this echo is removed is #1
and sent to conference room #2. Further, in the embodiment shown in FIG. 1, the case where four subtraction circuits are individually provided has been described, but seven subtraction circuits are shown in FIG. 2 as subtraction circuits. Using the same structure as the subtraction circuit shown in
Subtraction circuit 7■, and 7■ and 71! And 7! * may be integrated into two subtraction circuits, producing the same effect as the above embodiment.

【Effect of the invention】

As described above, according to the present invention, multiple speeds? For each combination of power and microphone, a pseudo echo signal corresponding to the loop from the relevant speaker power to the microphone is generated, and each echo is canceled by taking the difference between the generated pseudo echo signal and the transmitted signal. Therefore, a conference communication system using stereophonic sound that removes some of the echoes from multiple speakers to the microphones and makes it clear the positional relationship of the speakers, or where in multiple conference halls the speaker was speaking. This has the effect of providing an echo canceller device that can easily perform echo cancellation when applied to conference communication systems with multiple destinations.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an echo canceller device according to one embodiment of the invention, FIG. 2 is a block diagram showing another embodiment of the invention, and FIGS. 3 and 4 show conventional echo canceller devices. It is a block diagram. 2■2z is the speaker, 3,3■3t is the microphone, 6
■6. ,6■. 6+z. 6■,6. Is it pseudo-e? One generation circuit, 7. + 7 Ill 7 1■ 7■1,7. is a subtraction circuit, and 9.10 is an echo canceller device. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In an echo canceller device for canceling echoes that have passed from each of the speakers to the microphone in an acoustic system including a plurality of speakers for amplifying and outputting a reception signal and a microphone for inputting a transmission signal, each of the speakers and the A pseudo-echo generation circuit is provided for each combination with a microphone to generate a pseudo-echo signal having acoustic characteristics according to the acoustic coupling of the combination of the speaker and the microphone. An echo canceller device comprising a subtraction circuit that takes a difference from a pseudo echo signal generated by a pseudo echo generation circuit.