JPH0595391A - Sound control device of radio telephone set - Google Patents

Abstract

PURPOSE:To make it possible to perform a clear call even at a place where environmental noise is loud by installing a noise level detection microphone at a different position from a transmission microphone and performing a transmission of the difference of a transmission microphone and a noise level detection microphone. CONSTITUTION:At the back side of a transmission microphone 3, a noise level detection microphone 4 is installed. The voice signals from microphones 3, 4 enters a difference device 12 via preamplifiers 10, 11 and the difference output is obtained. Thus, by taking the difference, the common noise entering the microphones 3, 4 is cancelled. This difference output is outputted to a variable gain amplifier 15. By a noise signal obtained by a noise signal detectors 13 and a control signal amplifier 14, the output is controlled so that it may be made smaller when the noise signal is large and it may be made larger when the noise signal is small. The transmission voice output which is obtained at this place and is not affected by noise is transmitted to a modulation circuit for radio equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice control device for a wireless telephone such as a cordless telephone, and more particularly to a voice control device for a wireless telephone in consideration of the ambient noise level in use.

[0002]

2. Description of the Related Art Wireless telephones are convenient for users in that they can be used anywhere as compared with fixed telephones. However, since the place of use is arbitrary, it is more susceptible to external noise than the fixed type, and often uses nerves for communication. The volume control in the conventional wireless telephone for achieving such an object is performed by switching the volume switching switch added to the telephone. The volume switching switch includes continuous switching and discrete switching, but in any case, the switch is manually performed by the caller based on the judgment of the caller itself.

[0003]

However, even if the volume switching switch is used, the transmission volume (gain of the transmission microphone amplifier) is constant. The voice S / N ratio of the sound is reduced and the intelligibility is deteriorated. In addition, when making a call in a place where the environmental noise is large, the operator thinks that his voice cannot be easily transmitted to the other party, and thus makes a loud voice transmission. The wireless telephone is provided with a limiter circuit so that the sideband of the radio wave used does not spread too much or the amplitude is not overmodulated. Therefore, when a loud voice is transmitted, the limiter is applied, the waveform of the voice is distorted, and the clarity is lowered. In such a case, the automatic gain control of the transmitting microphone is performed, but in the normal method, the signal input from the transmitting microphone is often detected and amplified to perform the gain control. Therefore, the control level fluctuates depending on the presence or absence of the transmitted voice, and the receiving level of the other party also interlocks with this and sounds unnatural.

It is an object of the present invention to provide a voice control device for a wireless telephone which can maintain a clear call even in a place where environmental noise is large.

[0005]

According to the present invention, a noise level detecting microphone is installed at a position different from that of a transmitting microphone, and a difference between the transmitting microphone and the noise level detecting microphone is set as a transmitting output. Item 1).

Further, according to the present invention, the noise level detecting microphone is set at the back position of the transmitting microphone (claim 2).

Further, according to the present invention, the gain of the variable gain amplifier for transmitting and the variable gain amplifier for receiving are controlled by the noise level detecting microphone output (claim 3).

[0008]

According to the present invention, the noise mixed in the transmitting microphone and the noise mixed in the noise level detecting microphone are canceled by the difference (claim 1).

Further, according to the present invention, since the noise level detecting microphone is installed in the rear position of the transmitting microphone, the noise level detecting microphone is less likely to mix the call voice, and only the noise is mixed in the same manner. It is suitable for noise removal (claim 2).

Further, according to the present invention, since the gains of the variable gain amplifiers for transmission and reception are changed according to the magnitude of noise, it is possible to make a call that is substantially unaffected by noise ( Claim 3).

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1A to 1C are diagrams showing an embodiment of a wireless telephone according to the present invention. 1A is a front view, FIG. 1B is a side view, and FIG. 1C is a rear view. The wireless telephone 1 includes a receiver 2 for reception, a microphone 3 for transmission, a push button 6,
Although the antenna 5 is provided, the present embodiment is characterized in that the noise level detecting microphone 4 is installed at the rear position of the transmitting microphone 3. The microphone 4 may have a performance equivalent to that of the transmitting microphone 3, but may be inferior in performance because it aims to detect only noise.

The reason for installing it on the back is that the voice of the caller is hard to reach, but noise can be detected in common as with the transmitting microphone 3. Here, the noise does not refer to the noise of the caller himself but to the environmental noise existing in the surrounding space and having relatively low directivity.

FIG. 2 shows an embodiment of the electric circuit in the telephone. In this embodiment, the preamplifiers 10 and 11, the differencer 12,
Detector 13, amplifier 14, variable gain amplifiers 15, 16,
It comprises a receiver amplifier 17, microphones 3 and 4, and a receiver 2. The preamplifiers 10 and 11 are amplifiers for the detection voices of the microphones 3 and 4 to have a small amplitude, and the outputs thereof are input to the differentiator 12 to obtain a difference output between them. By taking the difference, the noise that commonly enters the microphones 3 and 4 is canceled. This differential output is input to the variable gain amplifier 15. In this embodiment, this gain is detected by the detector 13 and the amplifier 1.
Based on the noise signal obtained in step 4, if the noise signal is large, the control is made to be small, and if the noise signal is small, the control is made to be large. As a result, a transmission voice output that is not affected by noise is obtained, and is transmitted to the modulation circuit for a wireless device and transmitted.

Further, the gain of the variable gain amplifier 16 on the receiving side is controlled to be large when the noise is large and small when the noise is small, contrary to the transmission. Thus, the received voice becomes clear voice that is not affected by noise and is easy to identify. The concept of the above gain control is shown in FIG.

It is conceivable that the voice of the caller may also be input to the microphone 4 installed on the back side, and therefore the difference output of the difference unit 12 may be slightly lower than the original sound level. In such a case, the gain control of the variable gain amplifier 15 may be made larger than that of the variable gain amplifier 16. Further, the installation position of the microphone 4 is not limited to the back side as long as it is close to the transmitting microphone 3 and the transmitted voice is difficult to input. Further, it may be configured such that it is difficult to input the transmitted voice.

[0016]

As described above, according to the present invention, it is possible to obtain a wireless telephone which is less susceptible to environmental noise in both transmission and reception.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a wireless telephone according to the present invention.

FIG. 2 is a diagram showing an embodiment of an electric circuit of the present invention.

FIG. 3 is a diagram showing a concept of variable gain control of the present invention.

[Explanation of symbols]

 1 wireless telephone 2 receiver for reception 3 microphone for transmission 4 microphone for noise level detection 5 difference device (subtractor) 15, 16 variable gain amplifier

Claims (3)

[Claims] 1. A noise level detecting microphone installed at a position different from the installation position of a transmitting microphone of a wireless telephone, and a difference means for calculating a difference between the transmitting microphone output and the noise level detecting microphone output. A voice control device for a radiotelephone, comprising: a transmitting unit that captures the difference as a transmission output and wirelessly outputs the output. 2. The installation position of the noise level detection microphone is on the rear side of the installation position of the transmission microphone.
Wireless phone voice control device. 3. A noise level detecting microphone installed on the rear side of the installation position of the transmitting microphone of the wireless telephone, and a difference means for obtaining a difference between the transmitting microphone output and the noise level detecting microphone output. A first variable gain amplifier for inputting the differential output; transmitting means for wirelessly transmitting the first variable gain amplifier output; a second variable gain amplifier for receiving a wireless reception radio input from the other side; When the noise level detecting microphone output is large, the gain of the first variable gain amplifier is reduced, the gain of the second variable gain amplifier is increased, and the gain of the second variable gain amplifier is increased. Sometimes the gain of the first variable gain amplifier is increased and the second variable gain amplifier is increased.
And a means for controlling the gain of the first and second variable gain amplifiers so as to reduce the gain of the variable gain amplifier of FIG.