Determination of acute noise effects using distortion product otoacoustic emissions

Because distortion product otoacoustic emissions (DPOAE) are the product of the effect of two sinus tones on the cochlea, a multitude of combinations regarding the amplitude and the frequency ratio of the primary tones exists. The goal of the present study was to directly compare different stimulus combinations described in the literature in the detection of acute noise trauma using DPOAE. In the present study, 13 volunteers were exposed for 1 h to noise that was equivalent to sound levels in a discotheque. Audiograms and distortion product otoacoustic emissions were measured before and after noise exposure using four different stimulus combinations. For three of these settings, L1 was 65 dB, L1-L2 was 25 dB and f2/f1 was varied and set to 1.22, 1.20 and 1.18. For the fourth setting, L1 was at 65 dB, whereas L1-L2 was at 10 dB (f2/f1 = 1.20). A second group of volunteers (n = 14) was measured using identical time periods and setting, but was not exposed to noise. The comparison of different stimulus combinations showed that the stimulus combination L1 = 65 dB and L1-L2 = 25 dB at f2/f1 = 1.18 was best suited for detecting a difference between noise-exposed and unexposed individuals.