Are reports of temporary threshold shift-like symptoms by humans with normal hearing associated with hidden hearing loss?

Forty-six subjects with normal hearing, mean age 20.2 years, were selected from 451 volunteers completing a questionnaire concerning hearing, exposure to noise, experiencing TTS-like symptoms, and speech understanding. Metrics quantifying reports of TTS-like symptoms were constructed from responses to questions concerning hearing immediately after noise exposure. Statistically significant deteriorations in scores on the Speech, Spatial and Qualities of Hearing Scale (SSQ) (Gatehouse & Noble, Int J Audiol 43, 85-99 (2004)) were found with increasing values of TTS metrics for all SSQ questions. Groups reporting TTS-like symptoms (“exposed”), and “controls” (with little / no noise exposure and no reports of TTS-like symptoms), were formed from the subject pool with mean hearing levels differing <2 dB from 250Hz—8kHz. There was no difference in mean word scores between groups in a Modified Rhyme test conducted in speech-spectrum shaped noise. However, the exposed group exhibited a statistically significant deterioration in threshold for detecting 4Hz amplitude modulation of a 500Hz carrier at 10 dB sensation level (SL) compared to controls, and an improvement at 50 dB SL. It thus appears that TTS-like symptoms reported by persons with normal hearing may be associated with subtle suprathreshold changes in auditory performance. [Work supported by NIOSH.]