An analysis of speech under stress using certain modulation features

An analysis of speech under stress using its amplitude and frequency modulation (AM and FM) characteristics has been carried out. From the preliminary results using actual stressed speech from an operational aviation emergency, stress, in general, appears to increase the modulation behavior in both AM and FM. In particular, the modulation characteristics become significantly more if the analysis (carrier) frequency is centered at one of the resonant frequencies of the vocal tract. Moreover, the spectra of AM envelopes show increasing peak frequencies with stress. The highest peak in the spectra of the demodulated instantaneous frequency and the AM envelope appear to track the fundamental frequency F0. Linear prediction model of the AM envelope also shows a peak at F0 regardless of the analysis (center) frequency; the peak does not be distinct at all center frequencies, however.