Determination of the Pure-Tone to Noise-Band Transfer Function for Audiometric Testing and Fit Testing of Hearing Protectors.

摘要

This report details the results of the Pure Tone to Noise Band Transfer Function project. The purpose of this project was to examine the transfer function for thresholds obtained under HDA200 circumaural earphones using pure tone, equivalent rectangular noise bands, and 1/3 octave noise bands to thresholds obtained using TDH-39P supra-aural earphones. The objective is to obtain both correction factors for thresholds and also identify any differences in the reliability of threshold estimates obtained via any of the four methods. The results of this project suggest that (1) for the stimuli and calibration used in this project, only small adjustments are possibly needed to reach equivalent TDH-39P thresholds, (2) pure tone thresholds obtained with HDA200 circumaural earphones have reliability equal to or better than those obtained using TDH-39P earphones, (3) the reliability of noise band thresholds improves with broader stimulus bandwidth and is either equal to or better than pure tone thresholds, and (4) frequency-specificity begins to decline with stimulus bandwidths over greater than one ERB, which could complicate early detection of focal hearing changes. We believe that there are two recommendations supported by this project. First, these data support a recommendation for the use of HDA200 earphones for audiometric monitoring. Second, these data support the use of noise bands, preferably ERB noises, as stimuli for audiometric monitoring.