Otoacoustic emissions and early detection of noise induced hearing loss

The idea that otoacoustic emissions (OAEs) can be used to perform an early detection of hearing loss is strongly supported by both theoretical considerations and experimental evidence. It is well-known that the amplitude of the transient evoked OAE (TEOAEs) is dominated by the contribution of the spectral components for which the cochlear amplifier is most effective (spontaneous or long-lasting OAEs). It is also well-known that the outer hair cells (OHCs) are the first part of the auditory system to be damaged by noise. Thus it is quite obvious to predict that mild cochlear damage due to the early effects of noise exposure could be detected by using OAE measurements. Hall and Lutman (1999) have shown that OAEs are indeed more sensitive than standard audiometry in a range of mild hearing loss, by taking into account the sensitivity and test-retest fluctuations of both techniques. Lucertini et al. (2002) have shown that TEOAE parameters can effectively discriminate not only between populations of normal and impaired subjects, but also between exposed and nonexposed to noise. Moleti et al. (2002) have further demonstrated that both linear and nonlinear TEOAEs can effectively be used for this task.