DynamicsCompressorNode.reduction

The reduction read-only property of the DynamicsCompressorNode interface is a float representing the amount of gain reduction currently applied by the compressor to the signal.

Intended for metering purposes, it returns a value in dB, or 0 (no gain reduction) if no signal is fed into the DynamicsCompressorNode. The range of this value is between -20 and 0 (in dB).

var audioCtx = new AudioContext();
var compressor = audioCtx.createDynamicsCompressor();
var myReduction = compressor.reduction;