Speech nonlinearities, modulations, and energy operators

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 Ψ(χ) and its discrete counterpart are applied. It is found that Ψ 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