Page 52 - 2018Fall

Hearing Thresholds of OAEs
advance the study of both normal hearing and hearing im- pairment. The discovery of OAEs certainly measures up to the ideal of being significant for both laboratory-based re- search in the hearing sciences and translational audiological applications in the clinic.
Even with the somewhat satisfactory success of evoked OAE assays, particularly with respect to newborn hearing screen- ing, emissions testing in general has been underutilized in clinical practice as a noninvasive check of cochlear dysfunc- tion. However, with the growth of the field’s knowledge base concerning emission-generating sources along with the development of more precise measurement systems, OAEs have the potential of becoming more efficient tests of such cochlear properties as nonlinearities, frequency tuning, in- ner and middle ear transmission, and medial efferent system regulation. Thus, given the complexity of cochlear-generat- ing mechanisms, unmixing the linear reflection and nonlin- ear distortion origins of DPOAEs, for example, may result in unique sensitivities to cochlear pathology (e.g., Abdala and Dhar, 2012). Furthermore, other approaches suggest that DPOAE components can come, in certain circumstances, from distant basal cochlear regions that are sometimes 1-1.5 octaves from the BM place tuned to the f2 test stimuli (Mar- tin et al., 2010). Such added contributions from greater fre- quency regions than anticipated may be better understood using such novel methods as measuring DPOAEs intraco- chlearly using a noninvasive assay (Martin et al., 2016).
Moreover, further development of in the ear canal calibra- tion systems (as shown in Figure 1) using compensatory methods will better limit intersubject variability by control- ling for the individual acoustics of different ear canals. And the use of swept-tone rather than discrete-tone presenta- tions promises to result in test times that are clinically ac- ceptable (e.g., Abdala et al., 2015). Together, these contem- porary views of OAEs promise to eventually result in more efficient and accurate assessments of hearing thresholds that pinpoint the site of lesion within the impaired cochlea. It is exciting to anticipate what is ahead for the clinical applica- tions of OAEs.
Acknowledgments
This work was supported in part by Grant DC-000613 from the National Institute on Deafness and Other Communica- tion Disorders, National Institutes of Health, and Veterans Af- fairs Rehabilitative Research and Development Service Grants C449R and C6212L, US Department of Veterans Affairs.
Biosketches
Brenda L. Lonsbury-Martin is a re- search professor in the Department of Otolaryngology and Head and Neck Surgery, Loma Linda University Health, and a research scientist in the Veterans Affairs Loma Linda Healthcare System, Loma Linda, CA. She has served on the
faculties of several academic institutions including the Bay- lor College of Medicine, the University of Miami, and the University of Colorado, Denver. For over 30 years, her labo- ratory has conducted research on otoacoustic emissions. Dr. Lonsbury-Martin, a fellow of the Acoustical Society of Amer- ica, currently chairs the Medals and Awards Committee and is a member of the Acoustics Today Editorial Board as well as an associate editor of The Journal of the Acoustical Society of America (JASA) and JASA-Express Letters.
Barden (Bart) B. Stagner is the labora- tory supervisor in the Glen K. Martin and Brenda L. Lonsbury-Martin Re- search Services laboratories at the Vet- erans Affairs Loma Linda Healthcare System, Loma Linda, CA. For over 30 years, he has been a major partner in
the laboratories’ study of both the fundamental mechanisms underlying the generation of otoacoustic emissions and their practical applications in clinical settings. Mr. Stagner received BA degrees in both English and biology from Rice University. He is a member of the Association for Research in Otolaryngology.
Glen K. Martin is a research scientist at the Veterans Affairs Loma Linda Health- care System and a research professor in Department of Otolaryngology and Head and Neck Surgery, Loma Linda University Helath, Loma Linda, CA. His primary research interests include the
early detection of hearing loss using otoacoustic emissions. For over 30 years, his laboratory has been developing and refining procedures to measure otoacoustic emissions for the evaluation, screening, and monitoring of hearing health. He is a member of the Acoustical Society of America, the American Auditory Society, the Association for Research in Otolaryngology, and the Society for Neuroscience.
50 | Acoustics Today | Fall 2017