DPOAE I/O Functions in Normal and Impaired Human Ears

DPOAE I/O Functions in Normal and Impaired Human Ears
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Patricia Dorn, Dawn Konrad-Martin,Stephen Neely, Douglas Keefe, EmilyCyr and Michael Gorga
09 January 2014

Summarized from JASA 110, pages 3119-3131

Level: Advanced

Numbers of Slides: 29

Total file size: 656 k

DPOAE input/output I/O functions were measured at 7 f2frequencies (1 to 8 kHz;f2/f1 =1.22) over a range of levels -5 to 95dBSPL in normal-hearing and hearing-impaired human ears. L1-L2was level dependent in order to produce the largest 2f1-f2 responses in normal ears. System distortion was determined by collecting DP data in six different acoustic cavities. These data were used to derive a multiple linear regression model to predict system distortion levels. The model was tested on cochlear-implant users and used to estimate system distortion in all other ears. At most but not all f2's, measurements in cochlear implant ears were consistent with model predictions. At all f2frequencies, the ears with normal auditory thresholds produced I/O functions characterized by compressive nonlinear regions at moderate levels, with more rapid growth at low and high stimulus levels. As auditory threshold increased, DPOAE threshold increased, accompanied by DPOAE amplitude reductions, notably over the range of levels where normal ears showed compression. The slope of the I/O function was steeper in impaired ears. The data from normal-hearing ears resembled direct measurements of basilar membrane displacement in lower animals. Data from ears with hearing loss showed that the compressive region was affected by cochlear damage; however, responses at high levels of stimulation resembled those observed in normal ears

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