Software Tools for Otoacoustic Emission Measurement
Joshua Hajicek, Speech-Language-Hearing Sciences
Faculty Advisor: Dr. Glenis Long
NML Awards: The History and Public Health Award (March 2014), The New Media Lab Digital Dissertation Award (April 2014)
Hearing loss may occur naturally as we age (presbycusis), from taking ototoxic drugs (i.e. cisplatin, neomycin, high doses of aspirin, etc.), or from prolonged exposure to noise. According to the National Institute of Health (2008), 26 million Americans suffer from permanent and irreversible noise-induced hearing loss related to their workplace or recreational activities. Moreover, hearing related injuries are the most common service related injuries in the U.S. The effect of hearing loss is devastating and debilitating yet there are no tools to monitor subclinical changes in hearing health. Though helpful, hearing aids and cochlear implants only partially restore hearing so the only option is to identify changes in hearing health before they become permanent. For simulations of hearing loss, please visit: http://sens.com/helps/demo01/helps_d01_demo_check_2.htm.
One way hearing health may be monitored is through Otoacoustic Emissions (OAEs). The purpose of the proposed project is to develop an OAE software application that could augment current hearing conservation practices and also be used for basic hearing research. OAEs are sounds emitted from healthy ears. OAEs originate within the cochlea (inner ear) arising from the process of cochlear amplification, which make low level sounds easier to perceive. Cochlear amplification is the result of thousands of tiny outer hair cells (see image) working in concert to amplify the motion of the basilar membrane, a membrane organized by frequency that spans the length of the cochlea. See http://www.youtube.com/watch?v=PeTriGTENoc for an introduction on how the ear works.
During the cochlea’s amplification process some of the energy outer hair cells generate is reflected/scattered back out of the ear where it can be measured with a small microphone placed in the ear canal. Over exposure to sound or ototoxic drugs temporarily or permanently damage or immobilize outer hair cells. Damage or immobilization therefore affects the levels of OAEs. If OAE measurements are sensitive enough, small changes in hearing health may be detected. Absent or low amplitude OAEs are a good indicator of noise induced hearing loss and can be used as differentially to identify smaller changes in hearing health, before damage becomes clinical. Current barriers limiting present OAE measurement paradigms from being incorporated into hearing conservation programs include lengthy test times, high measurement variability within individuals, and lack of software to track OAEs longitudinally. This current project seeks to design and implement a software platform that can be used to make rapid, sensitive, and efficient OAE measurements using swept tones and least squares fit analysis. See image below for a schematized vision of the necessary software components needed for this project.