JP3028866B2 - Handset side tone control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sidetone control circuit used for a handset (transmitter / receiver) such as a communication device and a telephone.

[0002]

2. Description of the Related Art In a handset of a communication device by voice,
By giving a certain amount of attenuation to the signal input from the microphone and feeding it back to the speaker of the same handset (this is called sidetone), the speaker can confirm his / her own voice and can easily talk. FIG. 3 is a block diagram showing an example of a conventional side tone control circuit. Conventionally, sidetone is controlled by a hybrid circuit within a broken line. Next, the signal flow will be described for each functional block. Microphone 31
Is input to the hybrid transformer 33
Sent to the line via On the other hand, the side sound signal b to which a predetermined amount of attenuation is given by the attenuator 32 is obtained.
4 is input. The received signal c from the line is simultaneously input to the adder 34 via the hybrid transformer 33, and the adder 34 outputs a signal d obtained by adding the two signals. This output signal d is radiated to the space by the speaker 35.

According to such a conventional side tone control circuit,
The input signal a is always given a predetermined amount of attenuation, and the side signal b
And the adder 34 adds the received signal c to the output signal d.
Becomes This operation is performed irrespective of whether the input signal a and the received signal c from the microphone include an audio signal or only noise.

[0004]

Therefore, when the level of the environmental noise input to the microphone 31 is large,
A side sound signal (noise) b having a large level proportional to the level of the environmental noise is superimposed on the other party's voice, which is the received signal c,
There is a disadvantage that clarity may be significantly reduced. If the fixed attenuation is set to a large value in order to avoid this, the speaker will not be able to confirm his or her uttered voice for feedback. The present invention relates to the conventional circuit, in order to eliminate the problem that the intelligibility of the received voice is reduced when the environmental noise level on the sender side is large, the present invention is also applicable to the case where the environmental noise level on the sender side is large. It is an object of the present invention to provide a side tone control circuit in which the intelligibility of the voice received by the other party does not decrease and the sender can surely confirm the voice uttered by the sender.

[0005]

Sidetone control circuit of transmission receiving instrument SUMMARY OF THE INVENTION The present invention is a call signal of the talker from the microphone of handset
Signal to the line, and the received signal from the other party
The side tone signal obtained by attenuating the call signal of
A side-tone control circuit of the handset configured to output from a speaker of the handset, wherein a call signal from the microphone is input and a side-tone signal attenuated according to an attenuation control signal is input to the adder. An attenuator, an A / D converter for digitizing a speech signal from the microphone and outputting a digital signal, and a level calculation for detecting a level of the speech signal from the microphone based on the digital signal from the A / D converter A voice / noise determiner for analyzing a digital signal from the A / D converter to determine either voice or noise for each predetermined section and outputting a signal indicating the result; When the signal is a signal indicating noise, the level calculated by the level calculator is large.
Reducing the amount of attenuation of the variable attenuator in response to a small
Output the attenuation control signal, and when the signal indicating the result is a signal indicating voice , the attenuation of the variable attenuator is reduced to a predetermined attenuation.
And an attenuation controller that outputs the attenuation control signal .

[0006]

FIG. 1 is a functional block diagram showing an embodiment of the present invention. Next, the operation of this embodiment will be described.

The signal e input from the microphone 1 is A
The digital signal f is converted into a digital signal f by the / D converter 2 and input to the voice / noise determiner 3 to determine whether or not the section has a voice input.
It is determined whether the section is only a noise section. As a result, a voice or noise flag g is output. At the same time, the level calculator 4 calculates the level of the input signal from the digitized input signal f and outputs the value h. The speech / noise decision unit 3 has already been put to practical use in digital mobile communication and the like, and is an effective speech detector even when background noise is relatively large. Analysis such as prediction analysis, pitch component,
The noise parameter is adapted to the power threshold from the spectrum fluctuation to determine whether it is speech or noise, and a flag indicating either of them is output.

The voice / noise flag g and the input signal level h
Is input to the attenuation controller 5, the following processing is performed. If the voice / noise flag g indicates the input of only noise, the input signal level h at that time, that is, the noise level is referred to. As shown in FIG. If the level is large, an attenuation control signal i that increases the attenuation is output. voice/
If the noise flag g indicates that there is a voice input, the input signal level h at that time is a voice signal level, so that the predetermined attenuation amount similar to the conventional circuit is obtained regardless of the magnitude of the input signal level h. And outputs an attenuation control signal i. The variable attenuator 6 gives a certain amount of attenuation to the input signal e in accordance with the attenuation amount control signal i and outputs it as the side sound signal j. The variable attenuator 6 has been put into practical use as an electronic continuous variable attenuator, and is also called a programmable attenuator. For example, if the input control voltage is 0 to 1
There are a type in which the amount of attenuation changes linearly from 0 V to about 0 to 40 dB, and a type in which the amount of attenuation changes from 0 to 65 dB in 1 dB steps according to digital data of the input control voltage. The side sound signal j is added to the adder 8.
And the reception signal k from the line via the hybrid transformer 7 is input. The two signals are added to form an output signal m, which is radiated into the space by the speaker 9.

As described above, according to the side tone control circuit according to the present invention, the amount of attenuation corresponding to the input signal level h when the environmental noise level, that is, the voice / noise flag g indicates the input of only noise, is given to the input signal e. Since the side signal j is added to the received signal k by the adder 8 to obtain an output signal m, even when the level of the environmental noise input to the microphone 1 is large, the side signal j is given a sufficient attenuation. So
Even if the received signal k is superimposed on the other party's voice, the intelligibility is not significantly reduced. When the input signal e from the microphone 1 is a voice signal, a predetermined amount of attenuation is given to the input signal e as in the conventional circuit to produce a side tone signal j. It does not hinder the confirmation of the confirmation.

[0010]

As described above in detail, according to the present invention, in a section where there is no voice input, the amount of side sound attenuation changes in accordance with the environmental noise level. Even if it is high, it is possible to reduce the adverse effect that the intelligibility of the voice received by the other party is reduced, and it is possible to keep the attenuation at a predetermined value in the section of the speaker's voice input as before. This has the effect that the speaker can surely confirm his / her uttered voice and does not hinder the utterance.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a side tone control circuit of the present invention.

FIG. 2 is a characteristic diagram illustrating a relationship between an environmental noise level and an attenuation amount according to the present invention.

FIG. 3 is a functional block diagram of a conventional circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 microphone 2 A / D converter 3 voice / noise determiner 4 level calculator 5 attenuation controller 6 variable attenuator 7 hybrid transformer 8 adder 9 speaker 31 microphone 32 attenuator 33 hybrid transformer 34 adder 35 speaker

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04M 1/58-1/60 H04M 1/00

Claims (1)

(57) [Claims] 1. The communication of a talker from a microphone of a handset.
Outgoing speech signal to the line, and
The sidetone signal, which is attenuated from the talk signal of the speaker, is added by the adder.
A side-tone control circuit of the handset configured to calculate and output the output from the speaker of the handset, wherein the side-tone signal to which the speech signal from the microphone is input and attenuated in accordance with the attenuation control signal is input to the adder A digital attenuator for converting a speech signal from the microphone and outputting a digital signal; and detecting a level of the speech signal from the microphone based on the digital signal from the A / D converter. A level calculator; a voice / noise determiner for analyzing a digital signal from the A / D converter to determine either voice or noise for each predetermined section and outputting a signal indicating the result; When the signal indicating the noise is a signal indicating the noise, the variable attenuator according to the magnitude of the level calculated by the level calculator.
Output the attenuation control signal for increasing or decreasing the amount of attenuation, and when the signal indicating the result is a signal indicating sound, the variable attenuation
Attenuation control such that the attenuation of the vessel becomes a predetermined attenuation
A side tone control circuit for a handset, comprising: an attenuation controller that outputs a signal .