Effects of noise and exercise on distortion product otoacoustic emissions

The effect of physical exercise on both distortion product otoacoustic emissions (DPOAE), and on the temporary effects of noise on human cochlear function was examined. Changes in DPOAEs were compared to changes in behavioural thresholds and the possible relation between contralateral suppression of DPOAEs and susceptibility to noise exposure was investigated. Békésy audiometry, tympanometry and DPOAEs were measured in 8 subjects on 3 separate occasions: before and after noise exposure; before and after exercise at 60% of maximal oxygen uptake (VO2max); and before and after a combination of noise exposure and exercise, all of 10 min duration. Noise exposure was third-octave band noise of 102 dB SPL centered at 2 kHz. The magnitude of the effect of noise exposure on DPOAE amplitude averaged in the 2-4 kHz range was comparable but weakly correlated to the magnitude of the temporary threshold shift (TTS) measured as the change in Békésy threshold at 3 kHz. There was no effect of physical exercise without noise exposure on either the Békésy threshold or the DPOAE amplitude. Physical exercise significantly increased the noise-induced TTS and the effect of noise exposure on DPOAE amplitude. A positive correlation was found between the temporary effect of noise exposure and the contralateral suppression effect on DPOAE amplitude.