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Frequency domain secondary pulse estimation

The traditional model of speech production models voiced speech signals as the output of a minimum phase linear filter excited by a periodic impulse train. There exists a body of evidence which suggests that there are actually additional, secondary pulses in the excitation. This thesis investigates a frequency domain technique for estimating the locations and amplitudes of these secondary pulses. The estimator operates directly on the measured phase of the speech signal spectrum. While the estimator is shown to perform reliably on synthetic waveforms produced by exciting a minimum phase filter with a periodic excitation consisting of primary and secondary pulses, it fails when used on actual speech or even synthetic speech with non-impulsive excitation. The reasons for this failure are found to lie in extreme sensitivity of the signal spectrum to inaccuracies of the linear model. The results of exploratory experiments involving frequency domain speech coding using secondary pulse phase modelling are also presented. Thesis Supervisor: Dr. Robert J. McAulay Title: Senior Staff Member, MIT Lincoln Laboratory