On the effect of stress on certain modulation parameters of speech

This paper reports the results of correlation between demodulated amplitude and frequency variations from the AM-FM speech model and the heart rate of a fighter aircraft flight controller. It has been found that the peak frequencies in the spectrum of the amplitude envelope of the model follow F0 regardless of the center frequency of analysis. This tracking of F0 gives a qualitative estimate of stress level – as measured by the heart rate – relative to a neutral state of stress, with no a priori knowledge of F0 or formants. Additionally, the mean values of F0 estimates at low and high heart rates increased significantly from those at neutral state. Formant tracking showed an increase in F3 at both high and low heart rates while F4 generally varied directly with heart rate.