The compressor alters the sound data according to the ratio of incoming level to outgoing level. The ratio determines how much attenuation should be done on the incoming signal when it exceeds the threshold. For example, at a ratio of 2:1, every 2 dB of level over the threshold results in 1 dB output from the compressor over the threshold level. With a ratio of 1:1, the compressor is essentially off.For more information, see Equalization and compression in Overview of SHAPE.