Date of Completion

6-15-2020

Embargo Period

12-12-2020

Keywords

Audiology, Hearing Science, Efferent, Noise, Suppression of Otoacoustic Emissions

Major Advisor

Erika Skoe, Ph.D.

Associate Advisor

Jennifer Tufts, Ph.D.

Associate Advisor

Douglas Oliver, Ph.D.

Field of Study

Speech, Language, and Hearing Sciences

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

It has been well-established that there is large variability between individuals’ vulnerability to noise-induced hearing loss (NIHL), but recent work has galvanized the auditory research and clinical communities to re-evaluate the physiologic and perceptual consequences of subclinical noise-induced damage in individuals that would traditionally be considered “normal hearing.” The auditory efferent system is one potential source of variation between individuals, and research in animal models indicates that strength of the medial olivocochlear reflex (MOCR) is predictive of vulnerability to noise damage because it suppresses cochlear gain. Therefore, it has been proposed that MOCR strength may be useful as a clinical tool to identify individuals who could benefit from targeted hearing conservation efforts before clinically-significant NIHL is evident on the audiogram. However, limited research on the MOCR in humans has explored the reliability of this measure over time intervals greater than one week, and the few studies that have investigated how noise exposure itself may induce changes in MOCR strength yield mixed results. In order to address these gaps, contralateral suppression of otoacoustic emissions were measured as an index of MOCR strength in audiometrically normal hearing young adults with diverse noise exposure histories over 5 test sessions. Suppression was found reliable within the majority of participants and noise exposure the day before testing was not related to small changes in suppression between sessions. Noise exposure the week before testing was not directly related to MOCR strength, but may undermine an MOCR enhancement in musicians, motivating further investigation of mechanisms by which musical training and noise exposure induce plasticity of the MOCR.

For a novel tool to successfully be translated from research to practice, perspectives from the potential clinical end-users is warranted. To evaluate audiologists’ receptiveness to MOCR and perception of need for a new tool to address subclinical hearing loss, a survey was distributed. Responses reveal valuable clinical perspectives for auditory researchers wishing to tailor their work for eventual clinical application. Integration of researchers’ and clinicians’ knowledge can direct work that ultimately benefits patient populations and the general public.

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