Dynamic-range compression using digital frequency warping

In this paper, a multi-channel dynamic-range compressor system using digital frequency warping is described. A frequency-warped finite-impulse response (FIR) filter is realized by replacing the filter unit delays with a cascade of all-pass filters. The appropriate design of the frequency warping gives a non-uniform frequency representation very close to the auditory Bark scale. The resultant compressor offers good frequency resolution combined with low time delay, and has a group delay-versus-frequency response that is independent of the compressor gains. Listening tests indicate that the compressor group delay effects will be inaudible for most listeners and speech sounds.