Average optimal DPOAE primary tone levels in normal-hearing adults

Objective: Despite great progress towards optimizing DPOAE primary tone characteristics, factors such as stimulus and intra-subject emission variability have not been addressed. The purpose of this study was to identify optimal primary tone level relationships when these sources of variability were acknowledged, and to identify any influences of test frequency. Design: Following coupler-based measurements assessing primary tone level stability, two experiments were conducted. In experiment 1, DPOAE test-retest reliability without probe replacement was measured for f(2) =1-6kHz with L-1=L-2= 65dB SPL. In experiment 2, optimal L-1-L-2 relationships were identified for f(2) =1-6kHz. For 20L(2)75dB SPL, L-1 was varied 15dB SPL above and below the recommendation of L-1 =0.4L(2)+39 [dB SPL]. Study sample: Eleven normal-hearing adults participated in experiment 1. Thirty normal-hearing adults participated in experiment 2. Results: Stimulus variability did not exceed 0.1dB SPL. DPOAE reliability testing revealed an across-frequency mean standard error of measurement of 0.52dB SPL. The average optimal L-1-L-2 relationship was described by L-1 =0.49L(2)+41 [dB SPL]. A significant effect of frequency was identified for 6kHz. Conclusion: Including relevant sources of variability improves internal validity of a primary tone level optimization formula.