A research for basic properties of distortion product otoacoustic emissions in normally hearing subjects

With ILO-92 Otodynamics Analyzer, distortion product otoacoustic emissions (DPOAEs) at the 2 f1-f2 frequency were recorded from 86 normally hearing ears in response to four groups of different primary levels (L1 = L2 = 75 dB SPL; L1 = L2 = 65 dB SPL; L1 = L2 = 60 dB SPL; L1 = 65 dB SPL, L2 = 50 dB SPL). The average DPOAEs-gram demonstrated a bilobed contour with two peaks at approximately 1.5 kHz and 5 kHz and "notch" between 2.5 kHz and 3 kHz. Moreover, the contour of DPOAEs-gram had no obvious changes with sex, ear or primary stimulus levels differences. While the primary levels increased, the amplitude of DPOAEs gradually increased, which was about 55-65 dB SPL below the primary levels. At each frequency from 1-6 kHz, statistical analysis showed that there existed significantly different DPOAEs level under four groups of different primary stimulus levels.