LOADING CHANGES IN TIME-BASED PARAMETERS OF GLOTTAL FLOW WAVE-FORMS IN DIFFERENT ERGONOMIC CONDITIONS

The effects of prolonged (5 x 45 min) reading in different environment al and ergonomic conditions on time-based glottal waveform parameters of normal female and male subjects (n = 80) were studied. The exposure groups (n = 5 females and males per cell) consisted of eight combinat ions of the following factors: (1) normal (<65 dB) or high (>65 dB) sp eech output level; (2) sitting or standing posture; (3) low (25 +/- 5% ) or high (65 +/- 5%) relative humidity of ambient air. Two rest (morn ing and noon) and three loading (two in the morning and one in the aft ernoon) samples were recorded and analyzed. The glottal waveforms were obtained by inverse filtering of the acoustical signal using an autom atic method. The following time-based parameters were analyzed from th e estimated glottal flow waveform: (1) length of fundamental period; ( 2) open quotient; (3) speed quotient, and (4) closing quotient. The an alysis was based on inverse filtering of the first stressed syllable o f 'paappa' words repeated 3 x 5 times with normal, maximally soft and maximally loud phonation. Humidity was a significant factor in servera l instances. The interactions between gender and the loading factors w ere striking.