Noise induced temporary otoacoustic emission shifts.

Otoacoustic emissions are considered to reflect the outer hair cell activity of the cochlea, which in turn is recognised as the site most affected by noise exposure. The purpose of this study was to assess temporary cochlear alterations following brief noise exposure. Twenty young male subjects were exposed to 10 minutes of white noise at 90 dB SL. Standard pure tone audiometry, along with click and distortion product otoacoustic emissions (CEOAEs and DPOAEs), were measured before and after the noise exposure. Auditory pure tone threshold shifts of the order of 15 dB were accompanied by temporary CEOAE shifts of the order of 3 dB. DPOAE thresholds were elevated by approximately 5 dB. A positive, significant, and relatively strong correlation was obtained between the CEOAE shifts and the pure tone temporary threshold shifts (TTSs). However, in a number of cases emission shifts were unaccompanied by notable TTSs. Emissions appear to be more sensitive to cochlear changes following noise exposure and therefore more appropriate for screening and monitoring ears at risk of noise induced hearing loss (NIHL). The objectivity of the measurements and the short test time required further enhance their usefulness as a cochlear measure.