COAE Thresholds 1. Effects of Equal-Amplitude Versus Subtraction Methods Research Article
Research Article  |   October 01, 1997
COAE Thresholds
 
Author Affiliations & Notes
  • Tracy S. Fitzgerald
    Department of Communication Sciences and Disorders Syracuse University New York
  • Beth A. Prieve
    Department of Communication Sciences and Disorders Syracuse University New York
Article Information
Hearing & Speech Perception / Acoustics / Hearing Disorders / Hearing / Research Articles
Research Article   |   October 01, 1997
COAE Thresholds
Journal of Speech, Language, and Hearing Research, October 1997, Vol. 40, 1164-1176. doi:10.1044/jslhr.4005.1164
History: Received September 8, 1995 , Accepted April 3, 1997
 
Journal of Speech, Language, and Hearing Research, October 1997, Vol. 40, 1164-1176. doi:10.1044/jslhr.4005.1164
History: Received September 8, 1995; Accepted April 3, 1997

Although research has demonstrated that click-evoked otoacoustic emissions (COAEs) elicited by high-level stimuli are useful for identifying hearing loss, the ability of COAEs to predict behavioral thresholds has not been adequately tested. Results of studies comparing COAE thresholds and behavioral thresholds have been equivocal, perhaps due to the need for a more rigorous approach to COAE threshold estimation. The present study was designed to address several methodological concerns in COAE threshold testing, particularly the effects of two methods of stimulus presentation on COAE testing and threshold calculation. In an attempt to make COAE threshold estimation consistent across participants, COAE threshold calculations were based on mean noise floor levels across participants. COAE and noise floor levels were measured in 15 participants using both equal-amplitude clicks and a subtraction method. Broadband COAEs were analyzed into 1/3 octave bands, so that input/output functions could be examined and COAE thresholds could be calculated for each 1/3 octave band. Comparison of the two stimulus methods indicated several differences. Mean noise floor levels for the equal-amplitude method were approximately 6 dB lower than those measured for the subtraction method across frequency. In many cases COAEs evoked using the equal-amplitude method were higher in amplitude than those evoked using the subtraction method. COAE thresholds measured using the equal-amplitude click stimuli were significantly lower than those measured using the subtraction method. The significantly higher thresholds obtained using the subtraction method may be attributed in part to the reduction of COAE amplitude by the subtraction procedure, and not merely to the higher noise level. Slopes of the input/output functions were not significantly different between the two stimulus methods. These results suggest that the equal-amplitude method is preferable for COAE threshold testing because lower noise floor and larger amplitude COAEs may be obtained in the same test time.

Acknowledgments
The authors would like to gratefully acknowledge Jennifer Horn and Leslie Sheldon for their assistance in data analysis and to thank Karen Doherty, Amy Horwitz, David Kemp, Evan Relkin, Pamela Souza, Lisa Stover, Christopher Turner, and an anonymous reviewer for their helpful comments during the various phases of this paper. Dr. Stephen T. Neely wrote the independent analysis program. Special thanks to all the participants in this study. Portions of this study were from the first author’s master’s thesis and were presented at the Seventeenth Midwinter Meeting of the Association for Research in Otolaryngology, February, 1994. This work was partially supported by a Research and Creative Project Grant from the Graduate School at Syracuse University and by NIDCD Grant #5R29 DC 02028-03.
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