Our research is concerned with increasing our knowledge of the human middle ear and cochlea based upon acoustic response testing in the ear canal. Such tests are inherently noninvasive and lend themselves to clinical utilization. One project examines new forms of otoacoustic emissions (OAE), which may provide a clearer understanding of mechanical processes on the basilar membrane. Particular emphasis has been placed on stimulus-frequency OAEs, which yield data similar to behavioral tests of hearing, and on measuring and interpreting transient-evoked OAEs at frequencies up to 16 kHz. A second project studies middle-ear mechanics using acoustical measurements and modeling. New screening and diagnostic tests of middle-ear function are in development that have clinical promise to improve assessment. Another project is studying models of auditory filter tuning based on minimum uncertainty in frequency and scale.
The laboratory is equipped with computers for PC-based data acquisition and hearing assessment, a lock-in amplifier and a broad selection of transducers for acoustic measurements. Located in the laboratory are two sound-attenuated booths to facilitate data collection.
Douglas Keefe, Ph.D. is an acoustical physicist who has worked in hearing research, musical acoustics and related signal processing, acoustics and vibration fields.
A wideband (WB) test battery of aural acoustic tests may improve the screening and diagnosis of middle-ear and cochlear dysfunction. The battery addresses current limitations in newborn hearing screening (NHS) and diagnostic programs; it may help identify adult ototoxic hearing loss and diagnose middle-ear disease in patients receiving middle-ear surgery. Testing is performed over frequencies important for speech perception, and either at ambient pressure or using WB tympanometry. The WB acoustic reflex test measures an infant’s threshold to improve the accuracy of NHS programs. A click-evoked otoacoustic emission (OAE) test assesses cochlear function using an extended bandwidth relative to clinical tests. Research is underway to assess whether adding a WB test battery to the initial and follow-up NHS exams improves the accuracy of detecting sensorineural and conductive hearing loss. Middle-ear problems detected in the initial NHS exam may predict middle-ear dysfunction in the first year of life, including infants with cranial-facial anomalies and developmental delays. Extended-bandwidth OAE tests may help detect hearing loss in adult cystic-fibrosis patients receiving ototoxic medications. Research is in progress to evaluate the accuracy of WB tests in differential diagnoses of otoscleroris and ossicular discontinuity in adult surgery patients. More basic research concerns the non-invasive testing and modeling of middle-ear and cochlear mechanics in humans.
The laboratory research is concerned with devising better ways to assess how the middle ear and inner ear function, and to find new techniques for identifying hearing loss in infants, young children, and adults. One project may improve the detection of middle-ear fluid in the ears of young children, a condition which is associated with the pain and discomfort of earaches in young children. Another project has special relevance for improving newborn hearing screening programs to detect hearing loss, by testing whether the middle ears of infants tested just hours after birth in the birthing hospital function differently from the middle ears of infants only a few days later. Improved methods of detecting hearing loss and related conditions are essential to referring children and adults to health specialists for rehabilitative services.
Experimental and theoretical studies of cochlear and middle-ear mechanics
Sanford, C.A., Keefe, D.H., Ellison, J.C., Fitzpatrick, D.F., and Gorga, M.P. (2010). Wideband acoustic transfer functions predict conductive hearing loss in children. American Auditory Society meeting, Scottsdale, AZ (March).
Keefe, D.H., Fitzpatrick, D.F., Ellison, J.C. (2010). Wideband tympanometric assessment of ear-canal volume and eardrum admittance. American Auditory Society meeting, Scottsdale, AZ (March).
Keefe, D.H., Fitzpatrick, D.F., Liu, Y.-W., Sanford, C.A., Gorga, M.P. (2009). Wideband middle-ear muscle reflex test in a test battery to predict middle-ear dysfunction. Middle-Ear Mechanics in Research and Otology, Stanford University, Palo Alto, CA (June).
Sanford, C.A., Keefe, D.H., Fitzpatrick, D.F., Gorga, M.P. (2009). Estimating forward and reverse ear-canal and middle-ear transmission in infants. American Auditory Society meeting, Scottsdale, AZ (March).
Keefe, D.H., Alexander, J.M., Fitzpatrick, D.F. (2009). Speech-evoked otoacoustic emissions elicited by speech in quiet and in noise. Abstracts 32nd Annual Midwinter Meeting Assoc. Res. Otolaryngol. #540, p. 183. Baltimore, MD (February).
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