Training in Wideband Tympanometry

Measurement of acoustic impedance and reflectance in the human ear canal

10 mins
07 February 2022


Summary of: Voss, S. E., & Allen, J. B. (1994). Measurement of acoustic impedance and reflectance in the human ear canalThe Journal of the Acoustical Society of America95(1), 372–384.

This article discusses the role of the ear canal and its properties when performing impedance and reflectance measurements. Acoustic impedance measurements were conducted in 10 healthy young (18-24 years old) adults. The average reflectance and standard deviation of reflectance was calculated. Significant subject variability in the magnitude of reflectance for the 10 ear canals was measured. The authors felt this variability was due to cochlear and middle ear impedance differences, however the variable length of the ear canal between the measurements point and the eardrum could also have an influence. The authors acknowledge that the ear static pressure was not known at the time of the measurements, and this may have also contributed to some variability in the measurements. The article discusses the important properties of reflectance and transmittance phase and the use of these properties in the further modelling of ear canal impedance or reflectance.


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