JP2965060B2 - 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 for canceling a line echo signal in voice communication.

[0002]

2. Description of the Related Art In a conventional echo canceller, an attenuator for suppressing a residual echo signal of the echo canceller,
A noise generator that generates a pseudo noise signal having the same level as the idle noise of the near-end transmission signal, an adder that adds the output signal of the attenuator and the output signal of the noise generator, and transmits the signal to the far end. There was provided a switch for switching a transmission signal between a residual echo signal of an echo canceller and an output signal of the adder.

A specific description will be given with reference to FIG. The received signal 2 from the far end is transmitted to the near end through the receiving circuit, reflected by the near-end 4-wire 2-wire converter, and received as an echo signal 9. In order to cancel the echo signal, an echo canceller 3 composed of an adaptive adaptive filter is provided. However, the amount of cancellation of the echo canceller is also finite, and the remaining signal to be erased is transmitted as a residual echo signal. This is suppressed by the attenuator 4,
At this time, the near-end idle noise signal 10 is also attenuated. A pseudo noise signal having the same level as the idle noise signal 10 is inserted by the noise generator 7 via the adder 5 and transmitted to the far end side. The switching unit 11 controlled by the control circuit 8 switches between the residual echo signal and the pseudo noise signal output from the adder 5 as shown in FIG. In the no-call state, the near-end idle noise signal 10
And in the single talk state from the far end speaker, a signal obtained by adding the signal obtained by attenuating the residual echo signal by the attenuator 4 and the pseudo noise signal sent from the noise generator 7 to the far end side I do. That is, like the signal at the point c in FIG. 4, the actual idle noise signal and the pseudo noise signal are switched. If the two sound qualities are different, the far-end speaker causes a sense of incongruity in the audibility when switching.

[0004]

At the time of transition from a single talk state in which only a voice signal arriving from the far end side exists to a state in which single talk ends and a no-talk state, a pseudo noise signal generated by a noise generator is used. Since it is possible to switch to the near-end idle noise signal, the difference in sound quality between the two signals causes the far-end speaker to feel uncomfortable at the time of the switching, deteriorating the communication quality.

[0005]

According to the present invention, a first attenuator for suppressing a residual echo signal output from an echo canceller and a near end are provided in an echo canceller apparatus for canceling an echo signal on a communication line. A noise generator for generating a pseudo noise signal having the same level as the idle noise signal of the side transmission signal; a second attenuator for attenuating the pseudo noise signal; an output signal of the first attenuator and the second
And an adder for adding the output signal of the attenuator and transmitting the added signal.

Further, according to the present invention, there is provided a control circuit connected to the first attenuator, the noise generator, and the second attenuator, the control circuit being remote from a no-communication state. When transiting to the single talk state where only the voice signal arriving from the end exists, the loss value of the second attenuator is eliminated, and the loss value of the first attenuator is set to an arbitrary value, and the single talk state is changed. Is controlled so that the loss value of the second attenuator is gradually increased and the loss value of the first attenuator is gradually reduced within an arbitrary time until the end of the communication and the no-communication state. The characteristic echo canceller device is obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing an embodiment of the echo canceller device according to the present invention, and FIG. 2 is a diagram showing a state change of a transmission signal in the echo canceller device of FIG.

In FIG. 1, an attenuator 6 is provided at an output of a noise generator 7, and the control circuit 8 controls the attenuator 6 and the attenuator 4. In the control, the loss value of the attenuator 4 is removed in the non-communication state as shown in FIG. 2, and the near-end idle noise signal is transmitted as the signal at the point a in the figure. If the transition to
The loss value of the attenuator 4 is given to eliminate the signal output at the point a, the loss value of the attenuator 6 is set to 0, and the pseudo noise signal from the noise generator 7 is output as the signal at the point b in the figure.

Further, when transitioning from single talk to a no-communication state, the loss value of the attenuator 4 is gradually reduced for a certain period of time (for example, 1 second) from the moment of the transition.
Conversely, the attenuator 6 gradually increases the loss value. In the signal obtained by adding the respective signals, the component from the pseudo noise signal to the actual idle noise signal gradually increases like the signal at the point c in FIG. Such control is performed by the control circuit 8.

[0010]

As described above, according to the present invention, when the state transition from the single talk state in which only the voice signal arriving from the far end side is present to the end of the single talk state and the no-talk state, the far end side It is possible to make the speaker feel uncomfortable and to improve the speech quality.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an echo canceller device according to the present invention.

FIG. 2 is a diagram showing a state change of a transmission signal in the apparatus of FIG.

FIG. 3 is a block diagram showing an embodiment of a conventional echo canceller device.

FIG. 4 is a diagram showing a state change of a transmission signal in the device of FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmission output signal 2 reception input signal 3 echo canceller 4, 6 attenuator 5 adder 7 noise generator 8 control circuit 9 echo signal 10 idle noise signal

Claims (3)

(57) [Claims] 1. An echo canceller for canceling an echo signal of a communication line, a first attenuator for suppressing a residual echo signal output from the echo canceller, and a same level as an idle noise signal of a near-end transmission signal. A noise generator for generating the pseudo noise signal, a second attenuator for attenuating the pseudo noise signal, an output signal of the first attenuator and an output signal of the second attenuator are added and transmitted. An echo canceller device comprising: 2. The first attenuator, the noise generator,
And a control circuit connected to the second attenuator, wherein the control circuit is configured to, when transiting from a no-speech state to a single-talk state in which only a voice signal arriving from the far end exists, the second While eliminating the loss value of the attenuator,
The loss value of the first attenuator is set to an arbitrary value.
2. The echo canceller device according to claim 1, wherein the loss value of the first attenuator is controlled to be gradually decreased while the loss value of the first attenuator is gradually increased. 3. The control circuit eliminates the loss value of the second attenuator and changes the loss value of the first attenuator to an arbitrary value when transitioning from the no-talk state to the single talk state. At the time of transition from single talk to the no-communication state, the loss value of the second attenuator is gradually increased within a certain time from the moment of the transition, and the loss of the first attenuator is simultaneously increased. The value is controlled so as to gradually decrease, and by performing such control, the discomfort caused by the difference in sound quality between the idle noise signal and the pseudo noise signal when the state changes from the single talk to the no-communication state is reduced. The echo canceller device according to claim 2, wherein: