JPS5970065A - Controlling circuit of voice - Google Patents

Abstract

PURPOSE:To compare the level of a false signal with that of a normalized signal to suppress the false signal by controlling a time constant circuit and a variable gain amplifier in a voice controlling circuit by threshold detected by signal controlling circuit. CONSTITUTION:The variable gain amplifiers 13-1, 13-2 amplify signals inputted from signal channels 3-1, 3-2 of the voice controlling device and threshold detectors 14-1, 14-2 detect the operating state of the amplifiers 13-1, 13-2, respectively. The outputs of the detectors 14-1, 14-2 actuate the 1st time constant circuits 15-1, 15-2 and the 2nd time constant circuits 16-1, 16-2. The outputs of the circuits 15-1, 15-2 connect switching circuits 2-1, 2-2 to output the input signals to a succeeding unit and control the opposite amplifiers 13-2, 13-1 so as to reduce their gain respectively. Thus, the signal levels between a false signal and a normalized signal can be compared by using the threshold of the signal detecting circuit to suppress the false signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an audio control circuit for a device such as a loudspeaker telephone in which there is mutual signal leakage between two or more audio signal channels.

FIG. 1 is a circuit configuration diagram for explaining a conventional audio control circuit. In the same figure, 1 is a control circuit, 2-1.2-
2 is a switch circuit that is controlled by a control signal from the control circuit 1 and makes the signal channel 3-1.3-2 conductive or non-conductive, which will be explained next; 3-1.3-2 is a switch circuit 2;
-1.2-2 is a signal channel that can send a signal to the output via 4-1.4-2 is an amplifier, 5 is a signal detection circuit, 6 is a time constant circuit, 7 is a time constant circuit 6 and a switch circuit 2 -1.
This is a driver circuit that drives 2-2.

In a conventional audio control circuit composed of such circuits, the signal detection circuit 5 has two signal channels 3-1.
The input level of 3-2 is monitored, and a signal is output to the time constant circuit 6 in order to make the signal channel with the higher level conductive, and the time constant circuit 6 is repeatedly rendered non-conductive due to conduction too frequently. The drying circuit 7 is controlled with a certain time constant to prevent the drying. The driver circuit 7 uses a switch circuit 2-1 to make the signal channel designated by the signal detection circuit 5 conductive and to make the other channels non-conductive.
, 2-2.

However, in reality, as shown in FIG. 2, a hybrid circuit 8, a microphone 9, and a speaker 10 are connected to the audio control circuit. It is inevitable that acoustic coupling 12 exists due to the sound output from microphone 10 being input to microphone 9. Moreover,
The false signal due to the leaky coupling 11 may have the same level as the normal input signal of the signal channel 3-2, and it is not uncommon for the false signal due to the acoustic coupling 12 to be much larger than the normal input signal of the signal channel 3-1.

Further, their combination involves a time delay, and under such conditions, in such a conventional audio control circuit, the signal detection circuit 5 can only compare the levels of the normal signal and the false signal. There was a drawback that it could easily malfunction.

In order to eliminate these drawbacks, the present invention focuses on utilizing threshold control of the time constant circuit, variable gain amplifier, and signal detection circuit in the audio control circuit, and makes it possible to suppress false signals. Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 3 is a circuit diagram for explaining the present invention in detail. In the same figure, 13-1' and 13-2 are variable gain amplifiers controlled by the first time constant circuit 15-1 and 15-2, respectively, and 1'4-1 and 14-2 are threshold voltages. Threshold control detector capable of operating the detection circuit or separating the detection circuit by controlling the
1 and 151-2 are switch circuits 2-1 and 2-2, respectively.
and a first time constant circuit that controls the variable gain amplifier 13-1.13-2, and a second time constant circuit that controls the threshold of the Noro-1, xe-2u threshold control detector 14-1. This is a time constant circuit. The other numbers are the same as those in FIG. 11.

In the audio control circuit constructed from such a circuit, a signal input to the signal channel 3-1 is amplified by the variable gain amplifier 13-1 in a high gain state, and is amplified by the threshold control detector 14-1 in an operating state. 1 and 2 detected, the detector 14
The output of -1 operates each time constant circuit of the first time constant circuit 15-1 and the second time constant circuit 16-1. The output of the first time constant circuit 15-1 is the output of this switch circuit 2-1.
conducts and outputs the input signal to the rear of the switch circuit 2-1, and the variable gain amplifier 13- of the other channel.
The gain of 2 is controlled to be small.

Further, the output of the second time constant circuit 16-1 controls the threshold of the threshold control detector 14-2 of another channel,
Even if a signal is input from the variable gain amplifier 13-2, it will not operate.

As explained above, according to the present invention, even if there is a false signal due to leakage in the hybrid circuit or acoustic coupling between the microphone and the speaker, the gain of the amplifiers of other channels other than the signal channel is lowered, so that it can be detected. When the circuit is difficult to operate for the time of the first time constant circuit 15-1 and the initial part of the signal channel, generally the part where the sound power is large, is present, the detection circuits of other channels are disconnected. Therefore, a false signal is not detected during the time of the second time constant circuit 16-1. Therefore, no operation is performed to separate the signal of the signal channel. It goes without saying that the 7t1 human input signal performs the same operation as described above from the perspective of the signal channel 3-2. In addition, in the example of an actual device, the first time constant circuit 15-1. No5-2 0
If set to 3 to 06 seconds, the switch circuit 271 is held during that time, so the power of the voice changes, and even if the voice signal level decreases, the call will not be interrupted in the middle of the conversation, and the leakage of the high-speed circuit and the sound will be prevented. False signals due to combination can be effectively suppressed. Moreover, the second time constant circuit 16-1.16-
If 2 is set to 0.1 to 0.2 seconds, this is a reasonable time to prohibit false signals when the voice is strong. Further, according to the present invention, the human voice is 70 to 80 dBSPL.
It is possible to operate even in extreme cases where the sound pressure of the speaker's sound is input to the microphone at a sound pressure of 90 to 100 dBsPL.

In this way, the present invention is resistant to malfunctions caused by acoustic coupling, so it is necessary that the microphone and speaker be placed close together or in the same housing, or that the speaker volume be high under high noise conditions. It is effective if used as a public address telephone.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram for explaining a conventional voice control circuit, Fig. 2 is an explanatory diagram of the connection that causes the malfunction in Fig. 1, and Fig. 3
The figure is a circuit configuration diagram for explaining the present invention in detail. 2-1.2-2...Switch circuit, 3-1.3-2.
...Signal channel, 13-1.13-2...Variable gain amplifier, 14-1.14-2...Threshold control detector, 15-1.15-2...First time constant circuit, 16-
1.16-2...Second time constant circuit. Figure 2 375-

Claims (1)

[Claims] In an audio control circuit that controls at least two or more audio signals to be conductive or non-conductive, the control circuit is provided with two types of time constant circuits for one audio signal, a fixed or variable time constant circuit, and a first The time created by the time constant circuit of
It is characterized by comprising means for reducing the amplifier gain of a control circuit that controls the audio signal so as to make the audio signal conductive and other audio signals non-conductive, and means made of a second time constant circuit. Voice control circuit.