The dependence of distortion product otoacoustic emissions on the frequency separation and the relative levels of the primary signals

Author

Robert K. Rogers

Date of Award

6-1905

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Speech and Hearing Science

Major Professor

James W. Thelin

Committee Members

Samuel Burchfield, Harold Peterson, Michael Sims

Abstract

The present study was conducted to evaluate the effects of signal conditions on distortion product otoacoustic emissions (DPOAEs). DPOAEs were recorded in response to the experimental signals from seven human subjects with normal auditory function in the test ear as determined by otoscopy, pure tone audiometry, tympanometry, ipsilateral acoustic-reflex thresholds, and DPOAEs. The signals used to elicit DPOAEs were tone pairs (the primary signals): one tone (F) was fixed in level and frequency in all experimental conditions (65 dB SPL at 2003 Hz); the second tone (Fv) was presented at 45, 55, and 65 dB SPL and at seven different frequency separations above and below F (ΔFs were 65, 75, 100, 200, 300, 400, and 500 Hz). For each experimental signal, DPOAEs were measured above and below the frequencies of the primary signals at 2F - Fv and 2Fv - F. The study was conducted to determine the dependence of DPOAEs on the location of Fv above and below F in frequency in conditions when F and Fv were equal and unequal in level. A second purpose was to study the dependence of DPOAE level on the location of DPOAE above and below the primary signals in frequency. The results showed that DPOAEs located above the primary signals in frequency were suppressed in level. For DPOAEs located below the primary signals, when the variable signal (Fv) was located above the fixed signal (F) in frequency, the levels of the DPOAEs were relatively unaffected by changes in the level of Fv or by increases in ΔF. Both effects were explained in terms of the motion of the traveling wave of the cochlear basilar membrane. DPOAE levels are reduced when they are located on the side of the primary signals with the gradually sloping traveling wave. DPOAE levels are increased when a low-level primary signal is located in the gradual slope of the traveling wave of a high-level primary signal.

Recommended Citation

Rogers, Robert K., "The dependence of distortion product otoacoustic emissions on the frequency separation and the relative levels of the primary signals. " PhD diss., University of Tennessee, 1905.
https://trace.tennessee.edu/utk_graddiss/10567