Sound pressure distribution in natural or artificial human ear canals in response to mechanical ossicular stimulation

Abstract

Otoacoustic emissions (OAEs) in the ear canal (EC) are produced by tympanic membrane (TM) and ossicular motion driven by the cochlea. Measurement of OAEs is complicated by nonuniformities in EC sound pressure, which may lead to misinterpretation. Human temporal bones were prepared by removing most of the cartilaginous EC or replacing the bony EC with an artificial EC. The incus was stimulated mechanically through the facial recess by a small piezoelectric actuator to produce TM motion. Sound pressures resulting from broadband stimuli were measured at ~70 locations along the TM surface (Ptm), in the tympanic ring plane 4-6 mm distal to the umbo (Pec), and along the EC axis. Ptm showed considerable transverse spatial variation in narrow frequency bands at frequencies as low as 5 kHz, in contrast to the simpler distribution when sound enters the EC from its lateral end. These transverse variations generally had dissipated at the tympanic ring plane. Longitudinal sound pressure variations along the EC axis we...