Acoustic characteristics of the hypopharynx between male and female: A magnetic resonance imaging-based study

The hypopharynx is crucial in defining the unique acoustic properties contributing to speaker identity. However, the acoustic influence of gender-specific morphological variations in the hypopharynx remains insufficiently explored. Previous studies have largely focused on the acoustic effects of the hypopharynx in male subjects but few for females. This study investigated gender-related acoustic differences in the hypopharynx using 3D vocal tract models reconstructed from the MRI datasets of three male and four female Chinese subjects. Finite-difference time-domain simulations were conducted to examine the acoustic contributions of the laryngeal cavity and bilateral piriform fossae through cavity occlusion experiments. By comparing vocal tract transfer functions and sound pressure distributions before and after occlusion, the study observed notable differences between the male and female subjects. The female subjects exhibited higher frequency of laryngeal cavity resonance and piriform fossae anti-resonance than the male subjects. Hypopharyngeal cavity occlusion in the female subjects showed broader frequency variability and greater amplitude fluctuations. The acoustic interaction between the laryngeal cavity and piriform fossae was found to be stronger in the female subjects. These differences may be attributable to the comparatively shorter vocal tract length and smaller hypopharyngeal dimensions observed in the female subjects.