Analysis of distortion product otoacoustic emission spectra in normal-hearing adults.

Purpose: To evaluate the ability of distortion product otoacoustic emission (DPOAE) spectral characteristics to distinguish between ears with variable hearing sensitivity within the normal range.

Method: Distortion product grams (DP-grams) were acquired with primary tones decremented in 1/8-octave steps and primary-tone levels presented at 65 dB SPL (L1) and 45 dB SPL (L2) across an f2 frequency range of 842-7996 Hz from 22 normal-hearing adults (44 ears). Hearing thresholds of ears classified in Group A (n = 22) were better than ears classified in Group B (n = 22). Examined parameters of the DP-grams included spectral peak occurrence, peak height, peak width, and DPOAE levels. Analyses of variance were conducted to determine whether DP-gram parameters differed between Group A and Group B.

Results: For the low-resolution DP-grams examined in this study, no significant between-group differences in peak occurrence, peak height, and peak width were observed. DPOAE levels were significantly higher in ears classified in Group A compared with ears classified in Group B in individuals with symmetrical hearing.

Conclusions: Although spectral peaks are evident in DP-grams acquired with low resolution of the primary tones, DPOAE levels are more effective in distinguishing ears with greater hearing sensitivity from less sensitive ears.