Otoacoustic emissions in industrial hearing loss assessment

Otoacoustic emissions (OAEs) are a sensitive and frequency-specific tool for assessing cochlear damage. Parameters of an OAE signal decrease at the frequency that approximately corresponds with the injured region. However, damage in the basal turn of the cochlea is important for signal processing and OAE generation in the higher cochlear partition. In workers exposed to noise, the amplitude of OAEs decreases at the frequencies characteristic for acoustic trauma. These changes may occur prior to the audiometric threshold shift, which supports the superiority of OAEs in early detection of noise-induced damage. Therefore, OAEs may be applied as a quantitative test for individual assessment and monitoring of industrial hearing loss. Otoacoustic emissions are an established screening tool in the examination of newborn and infant hearing. In addition, studies on adult patients demonstrate high sensitivity and specificity if applied in screening sensorineural hearing loss, especially with multivariate analyses engaged. OAEs may be used as a screening test in subjects with an increased risk of exposure to noise and in epidemiological studies on industrial and environmental noise effects. Although otoacoustic emissions have a remarkable advantage in the evaluation of industrial hearing loss, there are some doubts about their utility in hearing conservation programs. The legislation and financial compensation associated with the diagnosis of occupational illness are based on the quantitative "gold standard", pure-tone audiometry. In addition, as it is not possible to reproduce the audiogram precisely, the OAEs may not be currently applied as a reliable test of hearing loss in malingerers. However, in some countries where tinnitus is eligible for compensation, OAEs may indeed appear helpful in the reliable diagnosis of cochlear damage within the respective frequency range.