We are generally interested in hearing, hearing loss, and hearing healthcare. One major focus of our work is in understanding the physiology and biophysics related to sounds created in the inner ear (otoacoustic emissions). We record these sounds using small microphones placed in the ear and attempt to understand the workings of the inner ear by analyzing them in various ways. We are also keenly interested in using these sounds to detect malfunction of the ear at the earliest. A second major focus is on hearing healthcare delivery. Here we are interested in understanding why so few people seek hearing health care. Once we identify barriers to access, we attempt to devise tools and methods to remove these barriers, thereby improving the affordability and accessibility of hearing health care.

Research

Cochlear Mechanics and OAEs

Otoacoustic emissions (OAEs) provide a convenient noninvasive window into cochlear mechanics. OAEs also provide a tool that can be applied uniformly across species to explore and understand commonalities and differences. Finally, OAEs are ideally suited for clinical applications across all ages. Our study of OAEs as a window into cochlear mechanics forms the foundation upon which we build our applied research enterprise. In this specific area we are interested in how OAEs are generated and how they propagate out from the cochlea to the outer ear. We have investigated the origin of what has become known as cochlear fine structure or microstructure. The ultimate goal is to understand the normal function of the cochlea and then apply this knowledge to build accurate and sensitive clinical tools for detection of cochlear malfunction. Funded by NIH/NIDCD; ASHA Foundation; Knowles Hearing Center; American Hearing Research Foundation
  1. Dewey, JB, Dhar, S(2017)A common microstructure in behavioral hearing thresholds and stimulus-frequency otoacoustic emissions. J. Acoust. Soc. Am. 142 (5):3069.
  2. Dewey, JB, Dhar, S(2017)Profiles of Stimulus-Frequency Otoacoustic Emissions from 0.5 to 20 kHz in Humans. J. Assoc. Res. Otolaryngol. 18 (1):89-110.
  3. Zhao, W, Dewey, JB, Boothalingam, S, Dhar, S(2015)Efferent Modulation of Stimulus Frequency Otoacoustic Emission Fine Structure. Front Syst Neurosci 9 :168.
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Hearing Across the Lifespan

From before birth through every day of our lives, we count on our acute sense of hearing for life-critical functions. In this line of work we study the maturation and aging of hearing through the human lifespan. In particular we are interested in the changes in inner ear (cochlea) function. Over the last few years we have collaborated with developmental scientist Carolina Abdala (University of Souther California) to study the maturation of inner ear function in premature and term infants. In another collaboration with Northwestern colleague Jonathan Siegel, we have evaluated changes in inner ear function during middle age. While this major focus in our laboratory continues to reveal interesting new knowledge, we have already demonstrated remarkable changes in inner ear function much earlier in life than previously known. Our results seem to suggest that the human inner ear starts to show signs of age-related changes as early as the third decade of life and these changes accelerate in the next twenty years. This work has profound implications on when and how to deliver hearing health care. These findings also shed new light on the timeline of auditory aging.
  1. Souza, NN, Dhar, S, Neely, ST, Siegel, JH(2014)Comparison of nine methods to estimate ear-canal stimulus levels. J. Acoust. Soc. Am. 136 (4):1768-87.
  2. Poling, GL, Siegel, JH, Lee, J, Lee, J, Dhar, S(2014)Characteristics of the 2f(1)-f(2) distortion product otoacoustic emission in a normal hearing population. J. Acoust. Soc. Am. 135 (1):287-99.
  3. Poling, G, Lee, J, Siegel, J, Dhar, SClinical Utilisation of High-frequency DPOAEs. ENT Audiol News 21 (4):91-92.
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Hearing Healthcare

Hearing loss is incredibly prevalent, with one-in-three adults over the age of 65 suffering from disabling hearing loss, and even larger numbers experiencing mild or moderate loss. Along with collaborators at Northwestern University, University of Texas and the Mayo Clinic we are investigating health care for this growing population of individuals with hearing loss. We are seeking to improve access to care by removing barriers to entry, such as the medical waiver needed to purchase a hearing aid. Furthermore, we are developing research that will address the gaps in knowledge about hearing health care, focusing particularly on unrecognized barriers to care and the costs associated with the ongoing epidemic of hearing loss. Funded by NIH/NIDCD
  1. Kleindienst, SJ et al.(2017)Development and Initial Validation of a Consumer Questionnaire to Predict the Presence of Ear Disease. JAMA Otolaryngol Head Neck Surg 143 (10):983-989.
  2. Kleindienst, SJ et al.(2016)Identifying and Prioritizing Diseases Important for Detection in Adult Hearing Health Care. Am J Audiol 25 (3):224-31.
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Efferent Modulation of OAEs

An extensive neural network connects the auditory cortex downward to various parts of the peripheral auditory system. A portion of this neural network at the brainstem connects and reflexively affects outer hair cell activity in the cochlea thereby modulating cochlear gain. Cortical neural networks further influence the working of this reflexive neural mechanism providing cortical control of the peripheral hearing organ. We study this network and its effect on cochlear gain using otoacoustic emissions and other tools. Much of this work is at the stage of basic discovery of the phenomenology at this time but we are actively interested in extending our understanding to useful tools to gauge the functional relevance of this neural network. We have published work on the speed of this process of gain control. Work to understand the frequency tuning properties of this system and the interaction between cortical and brainstem networks is ongoing and has already led to interesting (and bewildering) findings.
  1. Zhao, W, Dewey, JB, Boothalingam, S, Dhar, S(2015)Efferent Modulation of Stimulus Frequency Otoacoustic Emission Fine Structure. Front Syst Neurosci 9 :168.
  2. Zhao, W, Dhar, S(2012)Frequency tuning of the contralateral medial olivocochlear reflex in humans. J. Neurophysiol. 108 (1):25-30.
  3. Zhao, W, Dhar, S(2011)Fast and slow effects of medial olivocochlear efferent activity in humans. PLoS ONE 6 (4):e18725.
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People

Sumitrajit (Sumit) Dhar

Sumitrajit (Sumit) Dhar

Principal Troublemaker

Sumit’s scientific interests include otoacoustic emissions, cochlear mechanics, and hearing health care.

Niall Klyn

Niall Klyn

Postdoctoral Fellow

Niall is trained in cognitive ethnomusicology and psychophysics. He leads our work in hearing health care delivery.

Samantha Stiepan

Samantha Stiepan

PhD Candidate

Samantha is a clinically trained audiologist. She is working on more accurate and sensitive clinical applications of otoacoustic emissions.

Uzma Shaheen Wilson

Uzma Shaheen Wilson

PhD Candidate

Uzma is a clinically trained audiologist. Her interests are in the mechanisms of otoacoustic emissions and their connection to cochlear mechanics.

Hilary MacCrae

Hilary MacCrae

Au.D. Student

Hilary is interested in clinical audiology and the development of more accurate diagnostic tests that can translate to the clinic.

Claire Letendre

Claire Letendre

Au.D. Student

Claire’s interests are in improving effective communication between healthcare professionals.

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48 million (20%) of Americans report some degree of hearing loss

Participate in Research

We are looking for research participants between 7 and 45 years of age. Our projects typically require filling out questionnaires and participating in measurements of your hearing. The hearing tests are all done using regular earbuds much like the kind you might use to listen to a music player or phone.
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Contact Us

Address: Auditory Research Laboratory; 2240 Campus Drive, Evanston, Illinois 60208
Phone: 847 467 0123