Application of the Temporary‐Threshold‐Shift Paradigm for Assessing Sound Transmission in the Auditory System during Vowel Production

Ten female subjects were exposed to a 110 dB SPL 1000‐Hz fatigue stimulus for 3 min. During the exposure time, the subjects repeatedly produced a voiced vowel, a whispered vowel, or performed a nonvoiced articulatory gesture representing a vowel without whispering. Pre‐ and postexposure thresholds were tracked with a Békésy‐type procedure for a stimulus $12 oct$ above the fatigue frequency. Temporary threshold shift (TTS) following voiced /a/ and /i/ vowel conditions was significantly less than that observed for corresponding whispered or nonvoiced conditions at each postexposure recovery time measured. The magnitude of these differences ranged from 9 dB at 10 sec to 3 dB at 3 min of recovery. The results strongly indicate that voiced‐vowel production impedes transmission and hence reduces the energy delivered to the cochlea from a 1000‐Hz fatigue stimulus as evidenced by the reduced TTS magnitudes associated with this condition. Two potential mechanisms are proposed to account for alteration in sound transmission during voiced‐vowel production. One mechanism involves possible middle‐ear muscle contraction during voiced‐speech production, and the other concerns the effects of inertial bone conduction during such conditions. [Supported in part by the Wisconsin Alumni Research Foundation.]