Patent US 4,661,981

A method of and apparatus for processing audio signals in which a measure of amplitude of audio signals in a selected time period is obtained. The audio signals for the selected time period are delayed until the measure of amplitude is obtained, and then the delayed audio signals are normalized using the measure of amplitude. High-frequency emphasis may be employed prior to obtaining the measure of amplitude. Alternatively, a multi-channel system can be employed for processing audio signals in limited frequency bands. The method and apparatus are applicable in a variety of applications including hearing aids, audio storage media, broadcast and public address systems, and voice communications such as telephone systems.