Early identification of noise- induced hearing loss: a pilot study on the use of distortion product otoacoustic emissions as an adjunct to screening audiometry in the mining industry

This study investigated the feasibility of using Distortion Product Otoacoustic Emission (DPOAE) testing as an adjunct to pure-tone screening audiometry in the annual medical surveillance environment commonly found in the South African platinum mining industry. Signal-to-noise (S/N) ratios of the DPOAE test results conducted at two venues by a trained technician, the degree of hearing loss in platinum employees, the correlation between screening audiometry hearing threshold levels (HTLs) and DPOAE levels, and the ability of the DPOAE test to identify early NIHL in these employees were evaluated. Most S/N ratios were within the acceptable levels of greater than 10 dBSPL, hearing levels were within the range of hearing that provide valid DPOAE levels, signifi cant correlations were found between the HTLs from the screening audiometry and DPOAE testing, and in 73% of the 100 ears tested early NIHL could be identifi ed before the pure-tone audiogram indicated evidence of hearing loss. This indicates that DPOAEs would be a feasible and useful an adjunct to pure-tone audiometry in this setting.