Improved hearing conservation in industry: More efficient implementation of distortion product otoacoustic emissions for accurate hearing status monitoring

Abstract

Preventing occupational hearing damage requires close monitoring of workers' hearing. Implementing Distortion Product Otoacoustic Emissions (DPOAEs) in-field is a sensitive and feasible approach provided that a combination of minimal measuring time and infrequent false-positives - i.e. cases where elevated background erroneously compromises DPOAEs - is found. This paper investigates how measurement time can be reduced by carefully selecting the tested frequency span, and how false-positives are minimized by comparing DPOAEs acquired in noise with DPOAE signals previously obtained in optimal test conditions. To test this, DPOAEs have been registered with a 1/8-octave band resolution from 841 Hz to 8000 Hz for 60 subjects, in quiet conditions and in white noise levels ranging from 54 dB(A) to 90 dB(A), with and without extra noise reduction Within-subject variation of DPOAEs in noisy conditions is assessed at different levels of background noise. Obtained test-retest statistics quantify normal variability and allow within normal working routines to follow-up on persons with DPOAEs falling outside this range. To increase efficiency, optimal frequency regions are addressed by investigating per frequency the intra-subject DPOAE signal variability and DPOAE noise level.