Wideband Absorbance and 226-Hz Tympanometry in the Prediction of Optimal Distortion Product Otoacoustic Emission Primary Tone Levels

Abstract

Purpose Distortion product otoacoustic emission (DPOAE) amplitude is sensitive to the primary tone level separation effective within the cochlea. Despite potential for middle ear sound transmission characteristics to affect this separation, no primary tone level optimization formula accounts for its influence. This study was conducted to determine if inclusion of ear- and frequency-specific immittance features improves primary tone level optimization formula performance beyond that achieved using a univariate, L 2 -based formula. Method For 30 adults with normal hearing, DPOAE, wideband absorbance, and 226-Hz tympanometry measures were completed. A mixed linear modeling technique, incorporating both primary tone and acoustic immittance features, was used to generate a multivariable formula for the middle ear–specific recommendation of primary tone level separations for f 2 = 1–6 kHz. The accuracy with which L 1OPT , or the L 1 observed to maximize DPOAE level for each given L 2 , could be predicted using the multivariable formula was then compared with that of a traditional, L 2 -based univariate formula for each individual ear. Results Use of the multivariable formula L 1 = 0.47 L 2 + 2.40 A + f 2param + 38 [dB SPL] resulted in significantly more accurate L 1OPT predictions than did the univariate formula L 1 = 0.49 L 2 + 41 [dB SPL]. Although average improvement was small, meaningful improvements were identified within individual ears, especially for f 2 = 1 and 6 kHz. Conclusion Incorporation of a wideband absorbance measure into a primary tone level optimization formula resulted in a minor average improvement in L 1OPT prediction accuracy when compared with a traditional univariate optimization formula. Further research is needed to identify characteristics of ears that might disproportionately benefit from the additional measure.