Sound calibration and distortion product otoacoustic emissions at high frequencies

J. H. Siegel*, E. T. Hirohata

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

78 Scopus citations

Abstract

Distortion product otoacoustic emissions offer the potential for assessing inner ear function at high frequencies. However, commonly employed methods for calibrating the acoustic system used in these studies can lead to errors of ± 20 dB or more in the estimate of eardrum sound pressure levels above 2-3 kHz [Siegel, J. Acoust. Soc. Am. 95, 2589-2597 (1994)]. We assessed the magnitude of these errors by measuring the distortion product emission 2f1-f2 (f1 < f2) in human subjects using either of two microphone locations to calibrate the stimulus. Either the emission probe microphone itself or a probe tube positioned near the eardrum were used in calibrations. The emissions collected with f1 in the vicinity of 5-7 kHz showed a pronounced peak in level relative to other stimulus frequencies when the emission probe was used for calibration. The peak at 5-7 kHz disappeared when the probe tube near the eardrum was used for calibration. The discrepancy in emission levels between the two calibration procedures was as large as 20 dB. The difference is attributed to the presence of standing waves in the ear canal. The systematic errors in estimating eardrum sound pressure level using the emission probe microphone undoubtedly contribute to the variability of emission measurements for high-frequency stimuli.

Original languageEnglish (US)
Pages (from-to)146-152
Number of pages7
JournalHearing research
Volume80
Issue number2
DOIs
StatePublished - Nov 1994

Keywords

  • Acoustic calibration
  • Distortion product
  • High-frequency
  • Ootoacoustic emissions

ASJC Scopus subject areas

  • Sensory Systems

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