The importance of high-frequency hearing in a medico-legal context

Abstract

People whose hearing is damaged by exposure to intense sounds, typically in noisy factories or during military service, often claim compensation. The most common complaint of such people is difficulty in understanding speech when background sounds are present. However, because direct measures of the intelligibility if speech in noise were perceived to be unreliable, compensation has traditionally been based on the audiogram. Exposure to intense sounds usually has its greatest effects on audiometric thresholds at 4, 6, and 8 kHz. However, in several countries, including the USA and the UK, compensation for occupational noise-induced hearing loss is usually calculated using the average of audiometric thresholds for selected frequencies up to 3 kHz, based on the implicit assumption that hearing loss for frequencies above 3 kHz has no material adverse consequences. In fact, several studies show that frequencies above 3 kHz are important for the perception of speech in background sounds and for sound localisation, especially for resolving front-back confusions. It is concluded that audiometric thresholds at 4 kHz and perhaps 6 kHz should be taken into account when assessing hearing in a medico-legal context. In addition, direct measures of the ability to understand speech in noise should be obtained.