Title

Examination of the 2f2-f1 distortion-product otoacoustic emission in normal-hearing and hearing-impaired ears and its potential for use in the detection of hearing loss

Date of Award

2001

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Communication Sciences and Disorders

Advisor(s)

Beth A. Prieve

Keywords

Normal-hearing, Ears, Hearing loss, Distortion product otoacoustic emissions

Subject Categories

Communication Sciences and Disorders | Medicine and Health Sciences | Speech Pathology and Audiology

Abstract

Although many distortion-product otoacoustic emissions (DPOAEs) may be measured in the ear canal in response to two pure tone stimuli, the majority of clinical studies have focused exclusively on the DPOAE with the largest amplitude, 2f1-f2. The present study investigated another DPOAE, 2f2-f1, in normal-hearing and hearing-impaired ears in an attempt to determine the following: (1) the optimal stimulus parameters for its measurement and (2) its potential for improving the ability to separate normal-hearing and hearing-impaired ears using DPOAEs measured at low-mid frequencies (below 2000 Hz). Two experiments were conducted with the first experiment preceding the second. In Experiment One, the effects of overall level, level separation, and frequency separation of the primaries on 2f2-f1 amplitude were evaluated in both normal-hearing and hearing-impaired ears for low-mid f2 frequencies (700-2000 Hz). Moderately high-level primaries (60-70 dB SPL) presented at equal levels or with f2 slightly larger than f1 were necessary to evoke a measurable 2f2-f1 DPOAE in a majority of the normal-hearing participants. The f2/f1 ratio that produced the highest 2f2-f1 levels across normal-hearing participants was approximately 1.08, a smaller ratio than the f2/f1 of 1.22 typically used to measure 2f1-f2. In Experiment Two, 2f2-f1 and 2f1-f2 were measured in a group of both normal-hearing and hearing-impaired ears using two sets of parameters: (1) the traditional parameters for 2f1-f2 testing (1.22, 65/55) and (2) parameters that yielded high presence of the 2f2-f1 DPOAE among the normal-hearing participants in Experiment One (1.073, 65/65). Although the new parameters from Experiment One did improve test performance for 2f2-f1 amplitude and signal-to-noise ratio compared to performance when the traditional parameters were used to record 2f2-f1, the ability to separate normal-hearing from hearing-impaired ears was not better than that achieved using 2f1-f2 measured with the traditional parameters. Improvements in test performance compared to the use of 2f1-f2 alone were achieved when the information from the two DPOAEs was combined, either by summing their amplitudes or using logistic regression analysis. However, the improvements were small and may not be worth the added test time of recording a second DPGram.

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