Characterizing Dual Transmission of the Middle Ear

Abstract

The tympanic membrane (TM) is a component of the middle ear that provides a forward pathway for external sound energy to efficiently propagate to the inner ear. It is well established that the sensory cells of the inner ear also actively generate force that improves the ear’s ability to encode sound. As a result, inner ears can create sound in the absence of external stimuli, known as spontaneous otoacoustic emissions (SOAE). These emissions leak back out through the middle ear in the reverse direction. We measured lizards’ TM motions using a sensitive laser Doppler vibrometer and report spontaneous TM motion with displacements as small as several picometers, along with their relationship to SOAE measured simultaneously from the contralateral ear. Further, we measured motions induced by external sounds and computed the associated transfer function, as well as mapped out how these motions vary across the surface of the TM.