TY - JOUR
T1 - Estimating the operating point of the cochlear transducer using low-frequency biased distortion products
AU - Brown, Daniel J.
AU - Hartsock, Jared J.
AU - Gill, Ruth M.
AU - Fitzgerald, Hillary E.
AU - Salt, Alec N.
N1 - Funding Information:
This study was supported by research Grant No. RO1 DC01368 from the National Institute on Deafness and Other Communication Disorders, National Institutes of Health and by a grant to D.J.B. from the Ménière’s Research Fund Group of New South Wales, Australia.
PY - 2009
Y1 - 2009
N2 - Distortion products in the cochlear microphonic (CM) and in the ear canal in the form of distortion product otoacoustic emissions (DPOAEs) are generated by nonlinear transduction in the cochlea and are related to the resting position of the organ of Corti (OC). A 4.8 Hz acoustic bias tone was used to displace the OC, while the relative amplitude and phase of distortion products evoked by a single tone [most often 500 Hz, 90 dB SPL (sound pressure level)] or two simultaneously presented tones (most often 4 kHz and 4.8 kHz, 80 dB SPL) were monitored. Electrical responses recorded from the round window, scala tympani and scala media of the basal turn, and acoustic emissions in the ear canal were simultaneously measured and compared during the bias. Bias-induced changes in the distortion products were similar to those predicted from computer models of a saturating transducer with a first-order Boltzmann distribution. Our results suggest that biased DPOAEs can be used to non-invasively estimate the OC displacement, producing a measurement equivalent to the transducer operating point obtained via Boltzmann analysis of the basal turn CM. Low-frequency biased DPOAEs might provide a diagnostic tool to objectively diagnose abnormal displacements of the OC, as might occur with endolymphatic hydrops.
AB - Distortion products in the cochlear microphonic (CM) and in the ear canal in the form of distortion product otoacoustic emissions (DPOAEs) are generated by nonlinear transduction in the cochlea and are related to the resting position of the organ of Corti (OC). A 4.8 Hz acoustic bias tone was used to displace the OC, while the relative amplitude and phase of distortion products evoked by a single tone [most often 500 Hz, 90 dB SPL (sound pressure level)] or two simultaneously presented tones (most often 4 kHz and 4.8 kHz, 80 dB SPL) were monitored. Electrical responses recorded from the round window, scala tympani and scala media of the basal turn, and acoustic emissions in the ear canal were simultaneously measured and compared during the bias. Bias-induced changes in the distortion products were similar to those predicted from computer models of a saturating transducer with a first-order Boltzmann distribution. Our results suggest that biased DPOAEs can be used to non-invasively estimate the OC displacement, producing a measurement equivalent to the transducer operating point obtained via Boltzmann analysis of the basal turn CM. Low-frequency biased DPOAEs might provide a diagnostic tool to objectively diagnose abnormal displacements of the OC, as might occur with endolymphatic hydrops.
UR - http://www.scopus.com/inward/record.url?scp=62949119033&partnerID=8YFLogxK
U2 - 10.1121/1.3083228
DO - 10.1121/1.3083228
M3 - Article
C2 - 19354389
AN - SCOPUS:62949119033
SN - 0001-4966
VL - 125
SP - 2129
EP - 2145
JO - Journal of the Acoustical Society of America
JF - Journal of the Acoustical Society of America
IS - 4
ER -