Factors that introduce intrasubject variability into ear-canal absorbance measurements

摘要

Wide band immittance measures can be useful in analyzing acoustic sound flow through the ear and also have diagnostic potential for the identification of conductive hearing loss as well as causes of conductive hearing loss. In order to interpret individual measurements, the variability in test-retest data must be described and quantified. Contributors to variability in ear-canal absorbance-based measurements are described here. These include: assumptions related to methodologies and issues related to the probe fit within the ear and potential acoustic leaks. Evidence suggests that variations in ear-canal cross sectional area or measurement location are small relative to variability within a population. Data are shown to suggest that the determination of the Thévenin equivalent of the ER-10C probe introduces minimal variability and is independent of the foam eartip itself. It is suggested that acoustic leaks in the coupling of the eartip to the ear canal lead to substantial variations and that this issue needs further work in terms of potential criteria to identify an acoustic leak. Additionally, test-retest data from the literature are reviewed.