The Dependence of the Distortion Product 2f1 – f2 on Primary Levels in Non-Impaired Human Ears The optimal intensity relation between the two primaries used to generate Distortion Product Otoacoustic Emissions (DPOAEs) in unimpaired human ears, over a clinically relevant intensity range, was evaluated using a commercially available clinical device. The ILO92 was used to determine the level of the DPOAE at 2f1 – f2 for ... Research Article
Research Article  |   December 01, 1998
The Dependence of the Distortion Product 2f1f2 on Primary Levels in Non-Impaired Human Ears
 
Author Affiliations & Notes
  • Sumit Dhar
    Purdue University West Lafayette, IN
  • Glenis R. Long
    Gallaudet University Washington, D.C.
  • N. Brandt Culpepper
    Gallaudet University Washington, D.C.
  • Contact author: Sumit Dhar, MS, Department of Audiology & Speech Sciences, Heavilon Hall, Purdue University, West Lafayette, IN 47907. Email: sumit@purdue.edu
Article Information
Hearing & Speech Perception / Acoustics / Hearing Disorders / Hearing / Research Articles
Research Article   |   December 01, 1998
The Dependence of the Distortion Product 2f1f2 on Primary Levels in Non-Impaired Human Ears
Journal of Speech, Language, and Hearing Research, December 1998, Vol. 41, 1307-1318. doi:10.1044/jslhr.4106.1307
History: Received January 28, 1998 , Accepted August 12, 1998
 
Journal of Speech, Language, and Hearing Research, December 1998, Vol. 41, 1307-1318. doi:10.1044/jslhr.4106.1307
History: Received January 28, 1998; Accepted August 12, 1998

The optimal intensity relation between the two primaries used to generate Distortion Product Otoacoustic Emissions (DPOAEs) in unimpaired human ears, over a clinically relevant intensity range, was evaluated using a commercially available clinical device. The ILO92 was used to determine the level of the DPOAE at 2f1f2 for 16 combinations of primary levels in the range of 40 to 80 dB SPL from 40 unimpaired, young adult ears. Data were collected between 1 and 6 kHz at 1, 1.5, 2, 3, 4, 5, and 6 kHz. The commonly used procedure of dropping data points less than 3 dB above the noise floor was compared to a power subtraction procedure. A multivariate ANOVA was performed to determine main effects of gender, ear, stimulus levels, frequencies, and interactions between stimulus levels and frequencies. An overall increase of DPOAE amplitude with increase in primary level was observed, along with a decrease of the optimal difference in primary levels as L2 was increased. Although the power subtraction and 3-dB drop paradigms yielded similar results at high stimulus levels, the power subtraction paradigm provided a more realistic indicator of DPOAE level when low level primaries were used. Possible mechanisms responsible for the level dependence of the optimal relationship between primaries and implications for clinical choice of primary levels are discussed.

Acknowledgments
The authors acknowledge the valuable input received from Drs. Ted Glattke, C. L. Talmadge, L. A. Shaffer, P. Dorn, C. G. Fowler, P. Piskorski, and two anonymous reviewers.
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