Vocal tract area functions from autoregressive analysis of two‐point acoustic data

Abstract

It is well known that the frequencies of the low‐order driving point impedance poles and zeros of the vocal tract can be used to determine a smoothed representation of the vocal tract area function. The impedance poles are congruent with the vocal tract formants; the pole frequencies are specified by the location of peaks in the speech spectrogram. The impedance zero frequencies are indirectly related to formant bandwidths. The bandwidths, however, are difficult to accurately measure from speech. A method is presented for estimating vocal tract impedance zero frequencies directly as the peaks of the transfer function relating the acoustic speech signal to the acceleration signal from a transducer taped to the skin of the neck at the thyroid notch. This transfer function is estimated from pressure and acceleration signals using an autoregressive technique. Area function reconstructions derived from estimated pole and zero frequencies from human speech are presented. [Work supported by NIH.]