Modeling diagnosis of the human middle ear.

Abstract

Tympanic membrane (TM) and ossicular (OSC) models have been studied for many years. Most are implemented in the frequency-domain via Kirchhoff’s equations. However, the frequency domain is less intuitive than the time-domain models and does not apply given non-linear phenomena. This research presents a human time-domain TM+OSC implementation, extending our cat model [J. Acoust. Soc. Am. 122, 918–931 (2007)] as a cascade of slightly missmatched transmission lines. The canal plane-wave volume velocity is uniformly distributed across the canal cross-section, and updated at ≈1 MHz (to accurately simulate sound propagation). The time-domain model includes both forward and backward waves, enabling for the first time, the computation of one-way delays, thus explaining why multi-modal propagation observed on the TM are not critical. Results are validated with data from normal and pathological ears. Additionally, comparisons between the acoustic impedance in living and dead (temporal bones) ears shows significant temporal-bone artifacts. Because of ear-dependent impedance missmatch, canal standing waves are observed. It is frequently assumed that the umbo pressure is the best reference pressure. In fact the “forward-pressure” P+ is a better estimate of the ideal reference, the cochlear pressure [J. Acoust. Soc. Am. 125, 1605–1611 (2009)].