Envelope Periodicity Detection

A simple nonlinear method for detecting the (fundamental) period of a complex signal is presented being based on the time‐envelope shape rather than on the fundamental spectral component; the described detector produces pulses coinciding approximately with the major peaks, or envelope maxima, of the input waveform. Though primarily developed for musicological purposes, the method is not limited specifically to that application. Fundamentals of the theory are given for an arbitrary periodic input function, and some characteristic quantities are derived, such as maximum level difference between second harmonic and fundamental permitted in a two component signal, and minimum level difference needed for a signal of interest superimposed on, or modulated by, an interfering inharmonically related sinusoid. The method is also briefly compared with the zero‐crossing detection, and a combination of linear filtering with subsequent envelope periodicity detection is suggested. There are some common points between the operation of the described detector and auditory periodicity‐pitch detection.