Automatic level control of multiple audio signal sources

Abstract

An ambiance channel produces an ambiance audio signal as a reference threshold such as from a noise microphone located away from the program microphones. Variable gain amplifiers in a plurality of program channels selectively gate open those program channels that have audio present exceeding the ambiance threshold. When the program channels are below the noise threshold and hence inactive, they are gated off and the background noise in the ambiance channel is shunted around the program channel to the output. A control function circuit adjusts the gain of each of the program channels that have been opened as an inverse function of the number of open mics (called NOM). In another disclosed embodiment, a programmed microcomputer receives as inputs the status signals that represent the gated open or gated off conditions of the program channels. These status signals are processed by a software program in the microcomputer that performs both the functions of gating open individual program channels relative to the background noise level, and setting the gain of each of the program channels according to the NOM function.