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We investigate physiological measures of the auditory system. Our long-term goal is to improve the ability to diagnose hearing loss and other pathologies of the auditory system, particularly in infants and children. Current research focuses on measures that assess the function of the middle and inner ear.
Otoacoustic emissions
Otoacoustic emissions (OAEs) are soft sounds that are produced by the inner ear. Many people are unaware that when the ear is functioning normally, it actually generates some energy of its own. Some of this energy passes back out from the inner ear through the middle ear and into the ear canal where we can measure it with a sensitive microphone and a computer. OAEs are present in most ears with normal-hearing, but not present in most ears with hearing loss. As a result, OAEs are a useful tool for screening for hearing loss in patients who cannot undergo a typical hearing test, such as infants.
The OAEs we measure in the ear canal are believed to be the product of energy from two different mechanisms, nonlinear distortion and linear coherent reflection. We are investigating ways to improve our ability to detect hearing loss and estimate hearing thresholds with distortion-product otoacoustic emissions (DPOAEs) by making detailed measures of these sounds and separating the contributions from the two mechanisms using IFFT analysis. This project is supported by a New Century Scholars Research Grant from the American Speech-Language-Hearing Foundation.
Other ongoing projects on otoacoustic emissions include:
Clinical Ph.D. student Maureen D'Antuono will be investigating the effects of clinical depression and sertraline on otoacoustic emissions and the auditory brainstem response test.
Au.D. student Krystal Stazik is examining changes in transient-evoked and distortion-product OAEs with visual attention.
Au.D. student Marquitta Merkison will be investigating suppression of otoacoustic emissions using modulated signals and speech. This project will be completed in collaboration with Dr. Monita Chatterjee.
Au.D. student Bria Johnson will be investigating otoacoustic emission suppression in individuals with and without spontaneous otoacoustic emissions.
We are also collaborating on a project exploring potential changes in DPOAEs in rhesus monkeys who are undergoing repeated MRI testing. This project is being conducted by Clinical Ph.D. student Kelly King and Dr. Carmen Brewer at the National Institute on Deafness and Other Communication Disorders (NIDCD) at the National Institutes of Health (NIH).
Middle Ear Wideband Reflectance
The middle ear is comprised of the eardrum (tympanic membrane) and the three, tiny bones (malleus, incus, & stapes) that transmit sound from the ear canal to the inner ear. Measures of middle ear reflectance look at how energy is passed through the middle ear.
In one project, we are examining how middle ear wideband reflectance measures change as we age. This project was supported by a Graduate Research Board Summer award from the University of Maryland, College Park.
Other reflectance projects include:
Au.D. student Meggin Petronis will be examining wideband reflectance and ototacoustic emissions in patients with a history of chronic middle ear infections.
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