Speech nonlinearities, modulations, and energy operators

Abstract

An AM-FM model for representing modulations in speech resonances is investigated. Specifically, an FM model is proposed for the time-varying formants whose amplitude varies as the envelope of an AM signal. To detect the modulations the energy operator Psi ( chi ) and its discrete counterpart are applied. It is found that Psi can approximately track the envelope of AM signals, the instantaneous frequency of FM signals, and the product of these two functions in the general case of AM-FM signals. Several experiments on the application of this AM-FM modeling to speech signals, band pass filtered via Gabor filters are reported.