Sound Activated Automatic Amplifier Mute Circuit

The following article presents a simple sound operated/activated amplifier muting circuit which enables the amplifier to silence itself as soon a voice or an external sound occurs across the detector MIC. The circuit was requested by Mr. Seok Sothea.

Technical Specifications

I want to make a circuit about voice interrupt music..this circuit consists of two input, audio input and mic, and one output to amplifier.

First, the input from any audio player. While playing, if their is any sound into microphone, audio will become mute. After the sound from microphone is stop, the audio will be increasing its volume rapidly to its initial volume for some seconds. So, can you guide me some sir?

This circuit is connected directly to amplifier, if possible it uses power supply from amplifier. I don't know that it is useful or not.

But just my idea, i think it make easy for one who control and playing the music, like in the party, club, FM station, or anywhere that play music as background sound, they don't need to decrease or increase the volume of music when they talk and stop to talk on microphone.

The Design

Referring to the shown sound activated amplifier mute circuit below, we see only a single opamp being used for the proposed actions.

The functioning may be understood with the help of the following discussion:

When a external sound hits the MIC, depending upon the setting of VR1, if this sound is strong enough to pull pin#2 potential below the set potential of pin#3, the output instantaneously goes high.

This momentary high charges up the 10uF/25V capacitor and also triggers the NPN BC547 transistor.

The transistors instantly pulls the amplifier input to ground causing the required silencing or muting of the amplifier output.

The above situation persists for a few seconds depending on the values of the 10u cap and the 100k base resistor.

The above may be altered as per requirement for either raising or reducing the mute period of the amplifier.

As the 10uF discharges, the transistor gradually inhibits its conduction thereby causing an exponential or slow rising switch ON of the amplifier until it restores and reaches its full volume.