The clinical utility of expressing hearing thresholds in terms of the forward-going sound pressure wave

Abstract

Objective: To assess the clinical utility of quantifying pure-tone hearing thresholds in terms of the forward-going sound pressure wave. Design: Sound pressure measurements in the ear canal were used to derive, with hearing threshold measurements, hearing thresholds expressed in terms of the forward-going sound pressure wave, hearing thresholds based on coupler-based calibration, and hearing thresholds expressed in terms of the sound pressure measured at the microphone. Study sample: Fifty-two adults, 18 to 34 years of age, served as the study group. Results: Audiogram configurations were similar up to 2000 Hz for the three expressions of hearing threshold, consistent with the ear canal acting as a simple volume up to this frequency. Above 2000 Hz, notable differences in hearing threshold were found, consistent with the acoustic input impedance of the ear differing from a rigid, hard-walled cavity. Repeat testing showed all three expressions of hearing threshold to be repeatable. High density measurements of hearing threshold from 3000 to 6000 Hz provided qualified support for the derivation of the forward-going sound pressure wave. Conclusions: Hearing thresholds expressed in terms of the forward-going sound pressure wave are repeatable, and with in-situ calibration, may be superior to the current coupler-based method.