Wideband reflectance tympanometry in chinchillas and humans

Wideband reflectance tympanometry was performed on twelve chinchillas ears. The complex input impedance of the middle ear, multifrequency admittance t ympanograms, reflectance patterns (reflectance versus frequency), and refle ctance tympanograms (reflectance versus ear-canal air pressure) were analyz ed and compared to human data. The complex impedance of the chinchilla ear has a lower stiffness reactance at low frequencies, a higher mass reactance at high frequencies, and a lower resistance compared to the human. Multifr equency admittance tympanograms from chinchillas follow the same sequence o f patterns as humans for low frequencies (<2 kHz). At higher frequencies ty mpanograms from both species are poorly organized and do not follow a consi stent sequence of patterns. Reflectance patterns of chinchillas and humans are different. However, both species show high reflectance at low frequenci es, regions of lower reflectance in mid-frequencies (2-6 kHz), and high ref lectance at high frequencies (>8 kHz). Reflectance tympanograms for the two species show a single, centrally located minimum at low frequencies (<2 kH z) and are substantially different at higher frequencies. Results are shown for two animals that underwent eustachian tube obstruction. Reflectance pa tterns obtained with different ear-canal air pressures are substantially di fferent. Reflectance results at any single ear-canal pressure (including am bient pressure) do not completely characterize the effects of middle-ear pa thology. (C) 2001 Acoustical Society of America.