Clinical Applications of OAEs

Clinical Studies of Medial Olivocochlear Function

by Charles I. Berlin, PhD ;Linda Hood PhD ; Thierry Morlet, PhD; and Shanda Brashears, MCD

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Level: Intermediate

Abstract

The on-line lecture is an abridged version from a lecture Dr. Berlin presented during the ARO meeting of 2001. In this presentation, Dr. Berlin, summarizes several years of research on the medial efferent olivocochlearsystem (MOCS) in humans. Studies of otoacoustic emission suppression haveshown that the MOCS effect is reliable and valid and exits separately fromthe middle ear muscle reflex. Dr. Berlin explains what parameters should beused to elicit the medial olivocochlear reflex and what results should beexpected according to age and hearing condition. 

Level: Basic

Number of Slides: 12

Level: Intermediate

Numbers of Slides: 29

DPOAE I/O Functions in Normal and Impaired Human Ears

by Patricia Dorn, Dawn Konrad-Martin,Stephen Neely, Douglas Keefe, EmilyCyr and Michael Gorga

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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

DPOAE Suppression Tuning Curves in Normal and Impaired Human Ears

by Michael Gorga, Stephen T. Neely, Darcia Dierking, Patricia A. Dorn, Brenda Hoover, and Denis Fitzpatrick

Level: Advanced

Numbers of Slides: 58

Abstract:

Distortion product otoacoustic emission (DPOAE) suppression measurements were made in 20 subjects with normal hearing and 21 subjects with mild-to-moderate hearing loss. The probe consisted of two primary tones (f2,f1), with f2 held constant at 4 kHz and f2/f1 = 1.22. Primary levels (L1,L2) were set according to the equation L1=0.4L2 +39 dB (Kummer et al., J. Acoust. Soc. Am. 103, 3431-3444, 1998), withL2 ranging from 20 to 70 dB SPL (normal-hearing subjects) and 50 -70 dB SPL (subjects with hearing loss). Responses elicited by the probe were suppressed by a third tone (f3), varying in frequency from 1 octave below to 1/2 octave above f2. Suppressor level (L3) varied from 5 to 85 dB SPL. Responses in the presence of the suppressor were subtracted from the unsuppressed condition in order to convert the data into decrements (amount of suppression). The slopes of the decrement versus L3 functions were less steep for lower frequency suppressors and more steep for higher frequency suppressors in impaired ears. Suppression tuning curves, constructed by selecting the L3 that resulted in 3 dB of suppression as a function of f3, resulted in tuning curves that were similar in appearance for normal and impaired ears. Although variable,Q10 and QERB were slightly larger in impaired ears regardless of whether the comparisons were made at equivalent SPL or equivalent sensation levels (SL). Larger tip-to-tail differences were observed in ears with normal hearing when compared at either the same SPL or the same SL, with a much larger effect at similar SL. These results are consistent with the view that subjects with normal hearing and mild-to-moderate hearing loss have similar tuning around a frequency for which the hearing loss exists, but reduced cochlear-amplifier gain

Dr Gorga has made available also the original JASA articles from which the above presentation was based :



DPOAEs in Normal Ears

by Michael Gorga Ph.D. and Steve Neely D.Sc.

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Level: Intermediate

Numbers of Slides: 30

Level: Intermediate

Numbers of Slides: 18

Level: Intermediate

Numbers of Slides: 14

Level: Intermediate

Numbers of Slides: 26

Level: Intermediate

Numbers of Slides: 40

Abstract:

The lecture is supplemental material to the July-Augus-September 2003 editorial by Dr. Lalaki. The material was presented as a guest lecture during the 2003 6th EFAS meeting at Crete, Greece.

Level: Basic

Numbers of Slides: 24

Outcome Measures in Children with Auditory Neuropathy and Cochlear Implants

by Ann Peterson, M.A.; Jon Shallop, Ph.D.; Alyce Breneman, M.A.; Julie Babb, M.A.; Colin Driscoll, M.D.; Lee Fabry, M.A.; Ruth Stoeckel, M.A.

Level: Intermediate

Numbers of Slides: 34

Predicting Behavioral Thresholds From DPOAE I/O Functions

by Michael P. Gorga, Stephen T. Neely, Patricia A. Dorn, and Brenda M.Hoover

Summarized from JASA 113, pages 3275-3284

Level: Advanced

Numbers of Slides: 35

Abstract:

Recently, Boege and Janssen (J. Acoust. Soc. Am. 111, 1810 -1818, 2002) fit linear equations to distortion product otoacoustic emission DPOAE input/output I/O functions after the DPOAE level (in dB SPL) was converted into pressure (uPa). Significant correlations were observed between these DPOAE thresholds and audiometric thresholds. The present study extends their work by (1) evaluating the effect of frequency,(2) determining the behavioral thresholds in those conditions that did not meet inclusion criteria, and (3) including a wider range of stimulus levels. DPOAE I/O functions were measured in as many as 278 ears of subjects with normal and impaired hearing. Nine f2frequencies (500 to 8000 Hz in1/2-octave steps) were used, L2 ranged from 10 to 85 dB SPL(-5dB steps), and L1was set according to the equation L1 = 0.4L2 +39 dB (Kummer et al., J. Acoust. Soc. Am. 103, 3431-3444, 1998)# for L2l evels up to 65 dB SPL, beyond which L1 = L2. For the same conditions as those used by Boege and Janssen, we observed a frequency effect such that correlations were higher for mid-frequency threshold comparisons. In addition, a larger proportion of conditions not meeting inclusion criteria at mid and high frequencies had hearing losses exceeding 30 dB HL, compared to lower frequencies. These results suggest that DPOAE I/O functions can be used to predict audiometric thresholds with greater accuracy at mid and high frequencies, but only when certain inclusion criteria are met. When the SNR inclusion criterion is not met, the expected amount of hearing loss increases. Increasing the range of input levels from 20-65 dB SPL to 10-85 dB SPL increased the number of functions meeting inclusion criteria and increased the overall correlation between DPOAE and behavioral thresholds. 

Level: Intermediate

Numbers of Slides: 55

Abstract:

This is the abridged version of the course presented during the Master of Audiology at Ferrara University 1996.

TEOAE Suppression: Methods, Applications, Current Findings

by Linda J. Hood, Ph.D. and Shanda Brashears, M.C.D

Level: Intermediate

Abstract:

The on-line lecture is an abridged version from a lecture Dr. Hood presented during the American Academy of Audiology Conference meeting of 2003. 

 
 
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