Assessment of Middle Ear Function during the Acoustic Reflex Using Laser-Doppler Vibrometry
ARMY AEROMEDICAL RESEARCH LAB FORT RUCKER AL FORT RUCKER United States
Pagination or Media Count:
Over the past several years, recommendations have been made to update andor replace current military standards and regulations intended to protect individuals exposed to high-level acoustic impulses from hearing injury. One method recently implemented by the Department of Defense for determining the risk of hearing injury from impulsive noise exposures is the Auditory Hazard Assessment Algorithm for Humans AHAAH. The AHAAH is an electrical equivalence model of the human ear designed to reproduce sound transmission through the ear in order to predict potential hearing injury from a given sound exposure however, several key assumptions involving the effects of middle-ear muscle contraction MEMC on sound transmission through the middle ear during the acoustic reflex have not been validated. In the current study, we used laser-Doppler vibrometry LDV to measure tympanic membrane TM motion in response to an acoustic reflex-eliciting impulse as a proxy for assessing ossicular chain motion in human participants. Using this approach, we are able to directly measure the time course and magnitude of engaging the MEMC on middle ear movement. Changes in ossicular chain motion during MEMC were thus observed as frequency-dependent increases or decreases in TM velocity. Preliminary results suggest a more nuanced, across-frequency potential for middle ear gain or attenuation during the acoustic reflex.
- Anatomy and Physiology