Frequency selectivity in workers with noise-induced hearing loss

This study was undertaken in order to document, in a group of subjects affected by a noise-induced hearing loss, the relation between the loss of auditory sensitivity and the loss of frequency selectivity at mid-frequencies, namely 1000 and 3000 Hz. Auditory filter shapes were estimated using the notched noise method. Twelve notch widths were tested, six symmetrical and six asymmetrical with respect to the signal frequency; the spectral level of the noise was set at 50 dB SPL. Data were collected with 22 noise-exposed workers having different degrees of hearing loss. The findings indicate that above a certain degree of hearing loss, which seems to be around 30 dB HL, frequency selectivity tends to decrease linearly with increase in loss of sensitivity. Even when the degree of hearing loss is similar in origin and in magnitude, there is a wide variation among subjects in auditory filter bandwidth. Based on the data collected in this study, it is not possible to adequately predict the auditory filter bandwidth of an individual from hearing threshold levels.