Abstract: A sound mixing control system applicable to recording, broadcast and sound reinforcement systems. The gain provided for each input channel through the system is monitored, and whenever the sum of all the gains exceeds a threshold the overall gain is reduced to limit the sum of the gains to the threshold. Simultaneously the output level of the mixer is measured, and whenever the level would otherwise exceed a threshold the gains of the input channels are reduced in proportion to their individual levels to limit the output level to the desired maximum. Signals may be divided into multiple frequency bands, processed in parallel and recombined.

Abstract: In a sound reinforcement system having a plurality of input channels and input signal sources and at least one output channel, a gain control apparatus is provided for controlling the gain applied to the signals in each channel whereby the total gain of the system remains constant. Gain changes in each channel are proportional to signal ratios such that the automatic gain variations in all channels are always complementary. In a preferred embodiment, the control apparatus comprises means for providing a reference signal having a magnitude proportional to the sum of the amplitudes of the signals in the channels and a plurality of control signals each of which has a magnitude proportional to the amplitude of the signal in a respective one of said channels, and a plurality of attenuating means, each of which is responsive to the ratio of the corresponding one of said control signals to the reference signal.