Analysis of Measured and Simulated Supraglottal Acoustic Waves

Abstract

To date, while much attention has been paid to the estimation and modelling of the voice source (i.e. the glottal airflow volume velocity), the measurement and characterisation of the supraglottal pressure wave have been much less studied. Some previous results have unveiled that the supraglottal pressure wave has some spectral resonances similar to those of the voice pressure wave. This makes the supraglottal wave partially intelligible. While the explanation for such effect seems to be clearly related to the reflected pressure wave travelling upstream along the vocal tract, the influence that non-linear source-filter interaction has on it is not as clear. This paper provides an insight into this issue by comparing the acoustic analyses of measured and simulated supraglottal and voice waves. Simulations have been performed using a high-dimensional discrete vocal-fold model. Results of such comparative analysis indicate that spectral resonances in the supraglottal wave are mainly caused by the regressive pressure wave that travels upstream along the vocal tract and not by source-tract interaction. On the contrary and according to simulation results, source-tract interaction has a role in the loss of intelligibility that happens in the supraglottal wave with respect to the voice wave. This loss of intelligibility mainly corresponds to spectral differences around the frequency of the second formant.