Effects of prolonged oral reading on time-based glottal flow waveform parameters with special reference to gender differences.

The effects of prolonged (5 x 45 min) reading (loading) on time-based glottal waveform parameters of normal female and male subjects (n = 80) were studied. Two rest (morning and noon) and three loading (two in the morning and one in the afternoon) samples were recorded and analyzed. The glottal waveforms were obtained by inverse filtering of the acoustical signal using an automatic method. The following time-based parameters were analyzed from the estimated glottal flow waveform: (1) length of fundamental period (T); (2) open quotient (OQ); (3) speed quotient (SQ); (4) closing quotient (C1Q). The analysis was based on inverse filtering of the first stressed syllable of 'paappa' words produced with normal, maximally soft and maximally loud phonation. In the morning samples the loading affected only the T and OQ values of normal phonation in a statistically significant manner. In the afternoon all the quotient values changed statistically significantly in loud and normal phonation. On the basis of increased SQ and decreased C1Q values of females it is hypothesized that the female voices tended to change towards hyperfunction due to vocal loading.