The influence of eye colour on susceptibility to TTS in humans

In order to investigate the function of the inner ear melanin, noise-induced temporary hearing loss (temporary threshold shift, TTS) was studied in humans with either blue or brown iris colour. Sixty-eight normally hearing teenage boys participated in this study. Hearing thresholds before and after exposure were established with a computerized sweep frequency audiometer in the frequency range 0.8-8 kHz. The noise exposure consisted of a 1/3 octave band-filtered noise with centre frequency 2 kHz at 105 dB SPL for 10 min. The mean TTS in the frequency range 2-8 kHz showed a significant difference with the brown-eyed subjects developing least TTS, and the blue-eyed subjects most TTS.