Cochlear nonlinearity in normal-hearing subjects as inferredpsychophysically and from distortion-product otoacoustic emissions

摘要

The aim was to investigate the correlation between compression exponent, compression threshold,and cochlear gain for normal-hearing subjects as inferred from temporal masking curves (TMCs)and distortion-product otoacoustic emission (DPOAEs) input—output (I/O) curves. Care was givento reduce the influence of DPOAE fine structure on the DPOAE I/O curves. A high correlationbetween compression exponent estimates obtained with the two methods was found at 4 kHz but notat 0.5 and 1 kHz. One reason is that the DPOAE I/O curves show plateaus or notches that result inunexpectedly high compression estimates. Moderately high correlation was found betweencompression threshold estimates obtained with the two methods, although DPOAE-based valueswere around 7 dB lower than those based on TMCs. Both methods show that compression exponentand threshold are approximately constant across the frequency range from 0.5 to 4 kHz. Cochleargain as estimated from TMCs was found to be ~16 dB greater at 4 than at 0.5 kHz. In conclusion,DPOAEs and TMCs may be used interchangeably to infer precise individual nonlinear cochlearcharacteristics at 4 kHz, but it remains unclear that the same applies to lower frequencies.