JP2003318784A - Echo canceller system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an echo canceller system, capable of further reducing the remaining echo, without giving discomfort to a user. <P>SOLUTION: An echo canceller system comprises an adaptive filter 6, having a function to generate an estimated echo signal, with reference to a speech signal from a channel and estimate a transmission function between a microphone 1 and a speaker 7 from an actual remaining echo signal for updating a filter coefficient, and a subtracter 3 for subtracting the estimated echo signal from an actual echo signal inputted from a microphone 1. In the system, there is provided an acoustic mask processing means for removing components assumed to be masked in a audio signal from the channel by making use of aural characteristics. <P>COPYRIGHT: (C)2004,JPO

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 system applied to a hands-free device or a video conference system.

[0002]

2. Description of the Related Art Heretofore, as a technique for reducing the echo amount in an acoustic echo canceller system, a patent No. 0 has been proposed.
As disclosed in Japanese Patent No. 2861888, Japanese Patent Application Laid-Open No. 2000-59270 and Japanese Patent Application Laid-Open No. 2000-040985, it is common to adjust the input / output gain. Figure 5
FIG. 1 is a configuration diagram of a conventional echo canceller system. This echo canceller system performs a microphone 1, a sound volume control unit 2, a subtractor 3 for subtracting the calculated estimated echo and the actual echo, a sound volume control unit 4 for adjusting the gain sent to the line, and a process for reducing residual echo. The noise control unit 5, the adaptive filter 6 having a function of estimating the transfer function between the microphone 1 and the speaker, and automatically updating the filter coefficient, the speaker 7 transmitting the sound from the line, and adjusting the volume of the speaker 7. A volume controller 8 and a volume controller 10 for adjusting the gain of the sound from the line are provided. Each volume control block 2 in the figure,
When the optimum gain adjustment is performed at 4, 8, and 10, the amount of echo transmitted to the line is minimized. As another means for reducing the amount of echo, there is one that uses a directional microphone.

[0003]

However, when the gain is adjusted, the amount of echo is reduced, but a problem arises in that the sound is small and is difficult for the user to hear in actual use. Particularly, if the volume control unit 10 shown in FIG. 5 lowers the gain, the user A side becomes hard to hear, and if the volume control unit 4 lowers the gain, the user B side becomes harder to hear. Like this
Since the adjustment of the echo amount and the ease of listening for the user are contradictory,
There is a limit in gain adjustment alone. Therefore, it is considered that not only the gain of the echo amount is adjusted but also unnecessary sound that cannot be heard auditorily (sound that is masked by hearing) is removed. The sound generated from the speaker on the user A side is influenced by the transfer characteristics on the user A side, and thus a sound that should not be heard (hearing masked) may be input to the microphone. It is an object of the present invention to provide an echo canceller system capable of removing such an echo component and further reducing residual echo without causing discomfort to the user.

[0004]

In order to achieve the above object, the invention according to claim 1 generates an estimated echo signal by referring to a voice signal from a line, and uses a microphone from an actual residual echo signal. An echo canceller system having an adaptive filter having a function of estimating a transfer function between speakers and updating a filter coefficient, and a subtractor for subtracting an estimated echo signal from an actual echo signal input from a microphone. The echo canceller system having the auditory mask processing means for removing the component presumed to be masked in the voice signal from the line is the most important feature. A second aspect of the present invention is characterized in that, in the echo canceller system according to the first aspect, the echo canceller system which introduces continuous masking into the auditory mask processing by the auditory mask processing means is a main feature.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration diagram of an echo canceller system according to an embodiment of the present invention. This echo canceller system performs a microphone 1, a sound volume control unit 2, a subtractor 3 for subtracting the calculated estimated echo and the actual echo, a sound volume control unit 4 for adjusting the gain sent to the line, and a process for reducing residual echo. The noise control unit 5, the adaptive filter 6 having a function of estimating the transfer function between the microphone 1 and the speaker and automatically updating the filter coefficient, the speaker 7 transmitting the sound from the line, and adjusting the volume of the speaker 7. A volume control unit 8, a hearing mask processing unit 9 that removes unnecessary sounds that cannot be heard auditorily (sound that is masked by hearing), and a volume control unit 10 that adjusts the gain of the sound from the line are provided. First of all
An example of the echo canceling process will be described. The voice of the user B side transmitted from the line is first adjusted in gain by the volume control unit 10. Then, the hearing mask processing unit 9 causes the user A
Remove the components that are determined to be inaudible. here,
Simultaneous masking is used as the model to be removed. Simultaneous masking means an acoustic component to be masked as shown in FIG.
This is a model in which the masked acoustic component exists in the same region. The signal processed by the hearing mask processing unit 9 serves as a reference signal for the adaptive filter 6, is transmitted to the user A side, and after the volume is adjusted by the volume control unit 8, the signal is transmitted to the user A by the speaker 7. The sound generated from the speaker 7 is input as an actual echo from the microphone 1. Here, since the component in which this signal is determined to be inaudible to the user A is removed by the hearing mask processing unit 9, the component can be detected by the user B under the influence of the transfer characteristic on the side of the user A. It is never input as a real echo. Microphone 1
After that, the volume control unit 2 adjusts the gain of the signal from and the subtracter 3 subtracts the signal from the output of the adaptive filter 6. The subtracted signal becomes a residual echo, the gain of which is adjusted by the volume control unit 4, the noise of which is removed by the noise control unit 5, and the signal is transmitted to the line. Next, a second example of echo cancellation processing will be described. The voice of the user B side transmitted from the line is first adjusted in gain by the volume control unit 10. After that, the hearing mask processing unit 9 removes the component determined to be inaudible to the user A. Here, successive masking is used as the model to be removed. The successive masking is a model in which the masked acoustic component and the masked acoustic component have a temporal difference as shown in FIG. The case shown in FIG. 3 is when the sound to be masked is in front of the sound to be masked, which is called forward masking (forward masking). Also, as shown in FIG. 4, the masked sound may be after the masked sound. This is called retrograde masking (retrograde masking). The hearing mask processing unit 9 removes these components. The signal processed by the hearing mask processing unit 9 serves as a reference signal for the adaptive filter 6, is transmitted to the user A side, and is adjusted in volume by the volume control unit 8, and then the speaker 7
To user A. The sound generated from the speaker 7 is input as an actual echo from the microphone 1. Here, since the component in which this signal is determined to be inaudible to the user A is removed by the hearing mask processing unit 9, the component can be detected by the user B under the influence of the transfer characteristic on the side of the user A. It is never input as a real echo. The signal from the microphone 1 is then adjusted in gain by the volume controller 2, and subtracted from the output of the adaptive filter 6 by the subtractor 3.
The subtracted signal becomes a residual echo, the gain of which is adjusted by the volume control unit 4, the noise of which is removed by the noise control unit 5, and the signal is transmitted to the line.

[0006]

As is apparent from the above description, the present invention has the following effects.

In the echo canceller system according to the first aspect of the present invention, although the adjustment of the gain is the limit, it is possible to reduce the echo amount without giving a burden to the user by utilizing the auditory characteristics. As a result, the residual echo can be reduced. In the echo canceller system according to the second aspect, by using the successive masking, it is possible to further reduce the echo amount without imposing a burden on the user, and it is possible to reduce the residual echo.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of simultaneous masking.

FIG. 3 is an explanatory diagram of continuous masking (progressiveness).

FIG. 4 is an explanatory diagram of continuous masking (retrotropy).

FIG. 5 is a configuration diagram of a conventional echo canceller system.

[Explanation of symbols]

1 microphone 2 Volume control section 3 subtractor 4 Volume control section 5 Noise control section 6 Adaptive filter 7 speakers 8 Volume control section 9 Auditory mask processing unit (auditory mask processing means) 10 Volume control section

Claims (2)

[Claims] 1. An adaptive filter having a function of generating an estimated echo signal by referring to a voice signal from a line, estimating a transfer function between a microphone and a speaker from an actual residual echo signal, and updating a filter coefficient. And an echo canceller system having a subtractor for subtracting an estimated echo signal from an actual echo signal input from a microphone, utilizing an auditory characteristic to remove a component estimated to be masked in a voice signal from a line An echo canceller system having a hearing mask processing means for 2. The echo canceller system according to claim 1, wherein successive masking is introduced into the auditory mask processing by the auditory mask processing means.