Distortion product otoacoustic emissions: comparison of sequential versus simultaneous presentation of primary-tone pairs.

This Grason-Stadler GSI-60 system for measuring distortion product otoacoustic emissions (DPOAEs) allows the examiner to present one set of primary-tone pairs at a time (i.e., sequential presentation), or to present as many as four sets of primary-tone pairs at a time (i.e., simultaneous presentation). The Sequential and Simultaneous protocols were used to compare administration times, DPOAEs, and noise floors (NFs) on normal-hearing subjects at three frequencies (f2 = 1000, 2000, and 4000 Hz) and eight intensities (L1 = 40-75 dB SPL in 5 dB steps; L2 = 30-65 dB SPL). The Simultaneous protocol was completed in less than half the time (mean = 2 minutes, 21 seconds) required for the Sequential protocol (mean = 5 minutes, 13 seconds). When stimulus intensity (L1) was <60 dB SPL, the Sequential and Simultaneous protocols yielded similar DPOAEs and NFs. However, at the higher L1 intensities, the NFs for the Simultaneous protocol were larger than those for the Sequential protocol. The higher Simultaneous NFs reflect the greater system distortion/noise generated by the GSI-60 instrumentation. Reliability was assessed using the standard error of measurement of the difference between two scores. The data revealed no significant differences between protocols, and suggest that differences between two DPOAEs are statistically significant if they exceed approximately 7 dB (95% confidence interval).