Page ContentOverviewOur lab provides clinical and research services designed to understand cochlear processing and allow us to customize hearing aid characteristics for patients of all ages. The Human Sensory Physiology Laboratory divides its efforts between clinical service and research. Specific Areas of Research: Improving DPOAE test performancePredicting the magnitude of hearing loss from objective measurementsEstimating cochlear tuning, cochlear-amplifier gain, cochlear compression, and response growth from DPOAE suppression measurements in both normal-hearing and hearing-impaired human subjectsRelating objective and subjective measurements of response growthComparing response latencies from OAE and ABR measurements Clinical services include universal newborn hearing screening (UNHS) and diagnosing hearing loss in infants, young children, and patients with developmental disabilities. These screening and diagnostic assessments are based on measurements of distortion-product otoacoustic emissions (DPOAE) and auditory brainstem responses (ABR), including ABR assessments using toneburst stimuli. The research program focuses on both basic and translational research efforts designed to increase our understanding of cochlear processing in humans with normal hearing and those with hearing loss. A long-term goal of these efforts is to devise objective measures that will allow us to customize hearing-aid characteristics (such as compression threshold and compression ratio) for patients who are unable to describe their percepts of loudness.For Families The clinical program is dedicated to providing state-of-art evaluations of hearing for infants, young children and patients who are unable to provide voluntary responses during hearing tests. The research program is concerned with finding better ways to assess the hearing of infants and young children. With all babies being screened for hearing as part of their birth admission, babies with hearing loss are being identified very early in life. It is essential that we have accurate descriptions of their hearing problems so that we can design an appropriate course of intervention. It is important that intervention begin quickly because babies learn much about speech and language early in life by hearing the speech of others. Accurate descriptions of their hearing problems enable us to provide appropriate rehabilitation services, thus minimizing the impact of hearing loss on speech and language development. Children with developmental disabilities often have hearing loss, but are unable to participate in behavioral hearing tests. It is imperative for us to be able to describe any hearing problems these children may have so that appropriate intervention can be provided and these children will be able to participate in society to the fullest level. For these reasons, a major focus of both our clinical evaluations and research program is the development and implementation of improvements in how we diagnose hearing loss in infants and young children.For Clinicians and Scientists The research program focuses on cochlear nonlinearity in humans and on objective measures of threshold and suprathreshold consequences of hearing loss. Threshold studies are designed to more accurately identify ears with normal hearing and ears with hearing loss. Work currently under way or recently completed address issues such as: The effects of frequency and level on DPOAE test performanceOptimizing DPOAE test performance through the use of multivariate analyses, optimal stimulus conditions, stimulus paradigms that control source contribution, and improved calibration proceduresMeasurements of response growth based on DPOAE suppression measurements and the relation between these measurements and loudness growth in normal-hearing and hearing-impaired subjects Measurement of DPOAE suppression in normal-hearing and hearing-impaired subjectChanges in estimates of cochlear-amplifier gain and the gain-bandwidth tradeoff as a consequence of hearing lossBasic studies focus on:Issues associated with response growthCochlear-amplifier gainSource contributionDifferences in cochlear processing for high-frequency versus low-frequency stimuliSources of variability in DPOAE responses, suppression of DPOAE responses, determining optimal stimulus conditions for eliciting DPOAEsCalibration of stimuli, and relations between OAE and ABR latencies for the same stimuliTranslational research efforts focus on: Improvements in the diagnosis of hearing lossPredictions of threshold from objective measurements The consequences of hearing loss on indirect estimates of cochlear-amplifier gain Determining the extent to which objective measures of response growth correlate with subjective estimates of response growth, such as loudness, when hearing loss exists Facilities Clinical studies are performed in dedicated laboratories at Boys Town National Research Hospital. Clinical assessments are also performed at a satellite outpatient clinic, although all sedated ABRs are performed at the main hospital. Universal Newborn Hearing Screening is performed at an affiliated hospital at which there are 3000 births/year. The main clinical laboratory has a sound-isolated booth, two evoked-potential systems, one of which is portable and used for procedures conducted in inpatient rooms or the operating room. Additional equipment includes systems for DPOAE measurements and measurements of middle-ear function. The research laboratory has two double-walled sound booths, each equipped with a PC that houses two DMA-controlled 24-bit soundcards and specialized hardware that is used to measure DPOAEs. In addition, the laboratory is equipped with a clinical audiometer and a middle-ear analyzer. Additional PCs are used for data analyses, preparation of figures, and manuscript preparation.