JP3355594B2 - Echo canceller device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an echo canceller (apparatus) used in a public communication conference or the like.

[0002]

2. Description of the Related Art Conventionally, as an echo canceller device, a simulation circuit of an acoustic transmission system from when a sound is output from a speaker to when the sound is picked up by a microphone is formed, and an echo picked up by the microphone through a reception voice signal is sent to the simulation circuit. There is a technology that simulates the echo and subtracts the simulated echo from the voice including the actually picked-up echo to eliminate the echo. FIG. 7 is a diagram for explaining a conventional echo canceller 100 using a simulation circuit. 1 is a receiving voice input terminal, 2 is a speaker amplifier, 3 is a speaker, 4 is a transmitting voice output terminal, 5 is a microphone amplifier,
Reference numeral 6 denotes a microphone, 7 denotes an acoustic characteristic simulation unit, 8 denotes a subtractor, and 9 denotes an acoustic characteristic learning unit. The received voice signal R is input from the input terminal 1 and is amplified by the speaker 3. A part of the received voice RV that has been amplified is picked up by a microphone as an echo.
The simulation unit 7 simulates the sound transfer characteristics from the speaker 3 to the microphone 6. The subtractor 8 calculates the difference between the echo collected by the microphone 6 and the echo r simulated by the simulating unit 7 and cancels the echo. Generally, the acoustic characteristics of the space change due to the movement of the speaker, a change in temperature, and the like. Therefore, in order to maintain the accuracy of the simulation unit 7, it is necessary to constantly learn. In the prior art, the acoustic characteristic learning unit 9 considers the output of the subtracter 8 when the transmitted voice SV given to the microphone 6 is zero to be a remaining echo, and learns the acoustic characteristics using an adaptive filter so as to minimize it. Then, the acoustic characteristic simulation section 7 was updated.

[0003] However, in the case of double talk and use under noise, not only the echo of the received voice but also the transmitted voice and noise are superimposed on the output of the subtracter 8, so that the amount of remaining echo that cannot be erased cannot be observed. Learning cannot be performed, and the accuracy of the simulating unit 7 is deteriorated. Therefore, there is a disadvantage that the amount of echo cancellation is reduced. Also, when there is no received voice, there is no echo of the received voice for learning, so that learning cannot be performed, and the accuracy of the simulation circuit is reduced.

[0004]

In a conventional echo canceller using a simulation circuit, acoustic characteristics cannot be learned during double talk, non-received voice, or under noise with respect to spatial acoustic characteristics fluctuations. The accuracy of the simulation circuit deteriorates, and the amount of echo cancellation decreases. The present invention seeks to overcome these disadvantages.

[0005]

In order to achieve the above object, an echo canceller apparatus of the present invention has n receiving-side BPFs (band-pass filters) and m transmitting-side BPFs. The most important feature is that all (m + n) passbands of the BPF are differently selected.

[0006]

In the present invention, since the passbands of the n receiving BPFs and the m transmitting BPFs are all selected to be different, the received voice RV emitted from the speaker is echoed to the microphone as an echo. Even if the signal wraps around, the signal is suppressed by the transmitting-side BPF, and a signal with little echo is transmitted as the transmitting voice signal S. According to the present invention, echo cancellation is performed without using a circuit for learning or imitating the acoustic characteristics from the speaker to the microphone, so that echo can be reduced even during double talk, during non-received voice, and under noise. .

[0007]

(Embodiment 1) FIG. 1 is a diagram showing an embodiment of an echo canceller (apparatus) according to claim 1, in which parts corresponding to those in FIG.
A duplicate description is omitted. 10 is an adder on the receiving side, 11 is an adder on the transmitting side, 12 is a BPF (band-pass filter) group on the receiving side, and 13 is a BPF group on the transmitting side. BPF group 12
, And the total (m + n) passbands of the BPF group 13 are set to be different from each other. In order to operate the echo canceller shown in FIG. 1, the received voice signal R is passed by the BPF group 12 through pass bands respectively corresponding to n center frequencies f _R1 <f _R2 <... <F _Rn . Next, the outputs of the BPF group 12 are all added by the adder 10. Then, the echoes coming out of the speaker 13 and entering the microphone 6 are attenuated by the BPF group 13 on the transmission side having m center frequencies f _S1 <f _S2 <... <F _Sm different from the reception side. In order to further suppress the echo, the pass band of the BPF 12 is
It is desirable to set the respective frequency characteristics so as to be within the attenuation range of.

In general, since voice has a harmonic structure, if the center frequency f _R1 <f _R2 <... <F _Rn is selected as an integer ratio, the BPF group 13 is set so as to suppress these frequencies. , The harmonic component of the transmitted voice SV is BPF
There is a possibility of being blocked by the group 13. Therefore, each of the center frequencies f _R1 <f _R2 <... <F _Rn on the receiving side is a non-integer ratio, that is, f _Rj / f _Ri ≠ p (1−Δ) to p (1 + Δ) (1) (where i <j; i = 1, 2,..., n-1; j = 2, 3
.., N; p = 1, 2, 3,...).

Similarly, the transmission side center frequency f _S1 <f _S2 <...
If <f _Sm is selected as an integer ratio, the pass band of the BPF group 12 is set so as not to include these frequencies, and thus the BPF
Since the county 12 attenuates to some extent the same frequency as the frequency of the pass band of the BPF 13, the overtone component of the received voice signal R may be cut off by the BPF group 12. Therefore, the center frequency f _S1 <f _S2 <.
<F _Sm is a non-integer ratio to each other, that is, f _Sj / f _Si ≠ p (1−Δ) to p (1 + Δ) (2) (where i>j; j = 1, 2,..., M−1; j = 2,3
.., M; p = 1, 2, 3,...). In this way, it is possible to prevent the overtone component of the transmitted and received voice signal from being cut off.

The average value of the fundamental frequency of a male voice is 125
Hz (female voice is about twice this), standard deviation is 20.5 Hz (16.4)
%). The term (1 ± Δ) in the equations (1) and (2) takes into account that a certain setting range exists at the center frequency, but may be omitted. Usually, Δ may be selected from 0 to 0.2. (Embodiment 2) FIG. 2 is a view showing an embodiment of the second aspect of the present invention.
Parts corresponding to those in FIG. 7 are denoted by the same reference numerals, and redundant description will be omitted. A BPF center frequency control unit 14, a receiving-side fundamental frequency calculating unit 15, and a transmitting-side fundamental frequency calculating unit 16 are added to the configuration of FIG. In the receiving-side fundamental frequency calculator 15,
The basic frequency of the voice is calculated from the received voice signal R. The transmitting-side fundamental frequency calculator 16 calculates the fundamental frequency of the voice from the output of the microphone amplifier 5. The BPF center frequency control unit 14 calculates the center frequencies f _R1 , f _R2 ,..., F _{Rn of the} receiving-side BPF group 12 and the transmitting-side BPF group based on the calculated basic frequency of the receiving-side voice and the calculated basic frequency of the transmitting-side voice. Thirteen center frequency groups f _S1 , f _S2 ,..., F _Sm are set. Even when the center frequency is dynamically selected by the BPF center frequency control unit 14, the center frequency of the BPF 12 and the center frequency group of the BPF 13 are all selected so as to be different, and echo cancellation is performed.
In addition, the pass band width is selected by the BPF center frequency control unit 14 so that the power of the transmission voice signal passing through the BPF group 12 does not become too small and the reception voice passing through the receiving BPF group 12 does not become too small. Thus, the received voice and the transmitted voice other than the echo can be prevented from becoming too small.

(Embodiment 3) When conducting a multipoint conference or the like,
Since a plurality of microphones and a plurality of speakers are used, a multi-input multi-output echo canceller is required. However, since the multi-input multi-output echo characteristics are very complicated, an effective device has not been realized yet. The present invention does not perform learning of acoustic characteristics that become very complicated when multiple inputs and multiple outputs are performed, so that the present invention can be easily extended to multiple inputs and multiple outputs.

FIG. 3 is a diagram showing an embodiment of the invention of claim 5 , and uses the same reference numerals as in FIG. In this case, FIG.
Alternatively, the reception side circuits (all the same) of the echo canceller of FIG. 2 or FIG. 4 or FIG. 6 described later are provided for x channels and the transmission side circuits (all are the same) for y channels. Fourth Embodiment In general, a voice has a harmonic structure having a frequency component that is an integral multiple of a fundamental frequency. Even if a part of the harmonic component is missing, if the fundamental frequency is known, an integral harmonic component is interpolated. Can be restored. Therefore, by using this property of the voice, the voice component partially lost by the receiving-side BPF group and the transmitting-side BPF group can be restored, and high quality can be achieved.

FIG. 4 is a diagram showing an embodiment of the third aspect of the present invention, in which parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals, and redundant description will be omitted. FIG. 4 is obtained by adding a receiving-side voice band interpolating unit 17, a transmitting-side voice band interpolating unit 18, a receiving-side fundamental frequency calculating unit 15, and a transmitting-side fundamental frequency calculating unit 16 to FIG. The interpolation processing in the receiving voice band interpolating unit 17 and the transmitting voice band interpolating unit 18 can be realized as follows, for example. First, regarding the receiving side, the calculation unit 15 extracts the fundamental frequency and the frequency characteristic envelope of the received voice from the received voice signal R. The voice band interpolating unit 17 receives the BPF on the receiving side among the integral multiples of the fundamental frequency.
The frequency components cut off by the group 12 are interpolated by applying a frequency characteristic envelope to the fundamental frequency component. The same applies to the transmitting side from the voice collected by the microphone. Also, for example, “Nagafuchi et al.,“ Speech Enhancement / Suppression in Mixed Speech ”, IEICE Transactions A, Vol.J 62-A, No.
10, pp. 627-634 ". In FIG. 4, the receiving-side fundamental frequency calculator 15 calculates the receiving-sound fundamental frequency from the receiving-speech signal. Interpolation is performed by calculating the transmission voice fundamental frequency by the transmission fundamental frequency calculation unit 16 from the signal collected by the microphone and interpolating. However, only the reception voice band interpolation unit and the transmission voice band interpolation unit are used. It is also conceivable to interpolate with.

The echo canceller shown in FIG. 4 can also be used for howling suppression in a loudspeaker (PA) as shown in FIG. FIG. 5 shows the same operation as FIG. 4 except that an amplifier 19 is connected between the receiving voice signal input terminal 1 and the transmitting voice signal output terminal 4. The voice of the speaker to be loudspeaker picked up by the microphone passes through the BPF group 13, the adder 11, and the transmitting-side voice band interpolator 18, and is input to the amplifier 19 to be appropriately amplified, and the BPF group 12, the adder 10. The voice is amplified from the speaker 3 through the receiving-side voice band interpolation unit 17.

In a loudspeaker (PA), a transmitted voice SV picked up by a microphone 6 and a received voice RV picked up by a speaker 3 are output.
Are present at the same time, so that it is always in a double talk state. The conventional echo canceller is replaced with a loudspeaker (P
In the case of A), learning is not always possible because of the double talk state, and a voice switch for cutting off the receiving (transmitting) voice during transmitting (receiving) cannot be used. Therefore, the amount of echo cancellation is reduced due to fluctuations in acoustic characteristics, and howling occurs when the loop gain of the loudspeaker system increases,
It has no effect on howling suppression. However, in the echo canceller apparatus of the present invention, the echo can be canceled even in the double talk state, and the loop gain of the loudspeaker system is reduced, which is effective in howling suppression.

(Embodiment 5) In two-point communication, FIG.
Are installed at each point, the center frequencies f _R1 , f _R2 ,..., F _Rn of the BPF group 12 on the receiving side and the center frequencies f _S1 , f _S2 ,.
_{If Sm} and the echo canceller devices at both locations select the same,
The transmission voice signal S, which has passed through the transmission side BPF group 13 of the other party, is suppressed by the reception side BPF group 12, and communication is not possible. Therefore, it is conceivable that the center frequency groups to be used by each other are negotiated in advance when the line is connected, and the echo canceller devices at both points select different center frequency groups from each other and perform communication.

FIG. 6 is a diagram showing an embodiment of the fourth aspect of the present invention, in which parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals. FIG. 6 is the same operation as FIG. 1 except that the initial communication unit 20 and the BPF center frequency group control unit 14 are connected. In the initial communication unit 20, for example, a PB (push button) signal or a modem signal is used for an analog telephone line, or a data line is used for an ISDN line. Communication is performed to select mutually different center frequency groups.
The BPF center frequency control unit 14 sets the center frequencies of the BPF groups 12 and 13 based on the center frequency specified by the initial communication unit 20. In this way, it is possible to avoid selecting the same center frequency group as that of the other party by negotiation with the other apparatus at the initial stage of line connection. If the other party does not use the echo canceller of the present invention, there is no response from the other party for a certain period of time at the beginning of the line connection, so a predetermined standard center frequency group is selected.

[0018]

As described above, in the echo canceller apparatus of the present invention, each pass band of the BPF group 12 and the BP
Since echo cancellation is performed by selecting all (m + n) total passbands composed of the passbands of the F group 13 so as to be different from each other, the acoustic characteristic simulation unit required in the conventional echo canceller (FIG. 7). Further, the acoustic characteristic learning unit is not required, and the echo canceling function is not deteriorated even when the learning of the acoustic characteristics is difficult at the time of double talk, at the time of non-receiving voice, and under noise.

Further, the echo canceller apparatus of the present invention
It is also effective in suppressing howling in a loudspeaker (PA) used in theaters, concert halls, large conference halls, party halls, karaoke, and the like.

[Brief description of the drawings]

1 is a block diagram showing an embodiment of the present invention defined in claim 1.

FIG. 2 is a block diagram showing an embodiment of the invention of claim 2 ;

FIG. 3 is a block diagram showing an embodiment of the invention of claim 5 ;

FIG. 4 is a block diagram showing an embodiment of the invention of claim 3 ;

FIG. 5 is a block diagram of a loudspeaker (PA) using the echo canceller of FIG. 4;

FIG. 6 is a block diagram showing an embodiment of the invention of claim 4 ;

FIG. 7 is a block diagram illustrating a conventional technique using an acoustic characteristic simulation circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yutaka Nishino 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-7-22985 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B 3/00-3/44

Claims (5)

(57) [Claims] 1. A receiving side transmission circuit for transmitting a receiving voice signal input to a receiving voice input terminal to a speaker, and a transmitting side transmission for transmitting a transmitting voice signal picked up by a microphone to a transmitting voice output terminal. An echo canceller device inserted in the middle of a transmission / reception transmission circuit comprising a circuit and for canceling an echo generated when sound emitted from the speaker returns to the microphone through a space, wherein n (an integer of 2 or more) ) Receiving-side BPF (band-pass filter) means, receiving-side adding means for adding outputs of the receiving-side BPF means, and m (an integer of 2 or more) transmitting-side BPs
F means, and transmitting side adding means for adding outputs of the transmitting side BPF means, each pass band of said n receiving side BPF means and each passing band of said m transmitting side BPF means. Band (m +
n) Select this setting number of the pass band, the center frequency f _R1 of the n receiver side BPF unit <f _R2 <
.. <F _Rn and the ratio of each other is f _Rj / f _Ri ≠ p (where i <j; i = 1, 2,..., N−1; j = 2, 3)
.., N; p = 1, 2, 3,...) And the center of the m transmitting BPF means
The frequency f _S1 <f _S2 <... <F _Sm has a ratio f _Sj / f _Si ≠ p (where i <j; j = 1, 2,..., M−1; j = 2, 3)
..., m; p = 1,2,3, ...) and so as to choose that echo canceller apparatus according to claim. Wherein Oite to claim 1, and the reception-side fundamental frequency calculating means for calculating the fundamental frequency of the reception voice from the inputted reception voice signal, the fundamental frequency of the transmission voice from the input the microphone output The transmitting-side fundamental frequency calculating means for calculating, and the center frequencies f _R1 , f _R2 ,..., F _Rn of the n receiving-side BPF means are calculated from the calculated fundamental frequency of the received voice. From the fundamental frequency of the transmitted voice
Center frequency f _S1, f _S2 of pieces of the transmitter side BPF unit, ..., f
_And a BPF center frequency controller for controlling the value of _Sm . 3. Oite to claim 1, wherein the receiving side voice band interpolation to part of the receiver-side BPF frequency band of the signal is blocked by means synthesizes the signal of the frequency band that has passed through the BPF unit interpolation And at least one of a transmitting-side voice band interpolating means for synthesizing and interpolating a part of the signal of the frequency band cut off by the transmitting-side BPF means from the signal of the frequency band passing through the BPF means. An echo canceller device. 4. Oite to claim 1, the initial time of line connection, communicates with the partner apparatus, different center frequencies of the receiving side and the transmitting side BPF means and the center frequency of the counterpart of the echo canceller device Initial communication and center frequency selecting means for selecting a frequency, and B for setting and controlling the center frequencies of the receiving BPF means and the transmitting BPF means based on the selected center frequencies.
An echo canceller device comprising: a PF center frequency control unit; 5. A method according to claim 1 to the receiving side circuit of the echo canceller according to any one of 4 x (2 or more integer) channels (all the same configuration) and transmitting side circuit y (2 or more integer (2) An echo canceller device provided for each of the channels (all having the same configuration).