A reversible method for sound analysis adapted to bio-acoustical experiments.

The paper describes a method of sound analysis, 'modulation analysis', its implementation on a minicomputer PDP12 and some aspects of its application in bioacoustical experiments. Modulation analysis reversibly resolves a given sound signal into time-courses of amplitude and carrier frequency. Since time is preserved as the independent variable the method provides a suitable basis for the computer modification of sounds. Problems of practical performance are discussed with regard to sounds of birds and insects. Further, the use of sound modification in a neurophysiological study of the hearing system of birds is described.