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

• Published in: The Journal of the Acoustical Society of America Vol. 124; no. 4; p. 2149
• Main Authors: Johannesen, Peter T, Lopez-Poveda, Enrique A
• Format: Journal Article
• Language: English
• Published: United States 01.10.2008
• Subjects: Acoustic Stimulation; Adult; Auditory Threshold; Cochlea - physiology; Humans; Models, Biological; Nonlinear Dynamics; Otoacoustic Emissions, Spontaneous; Perceptual Masking; Pitch Perception; Psychoacoustics; Time Factors; Young Adult
• ISSN: 1520-8524
• DOI: 10.1121/1.2968692

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 given to reduce the influence of DPOAE fine structure on the DPOAE I/O curves. A high correlation between compression exponent estimates obtained with the two methods was found at 4 kHz but not at 0.5 and 1 kHz. One reason is that the DPOAE I/O curves show plateaus or notches that result in unexpectedly high compression estimates. Moderately high correlation was found between compression threshold estimates obtained with the two methods, although DPOAE-based values were around 7 dB lower than those based on TMCs. Both methods show that compression exponent and threshold are approximately constant across the frequency range from 0.5 to 4 kHz. Cochlear gain as estimated from TMCs was found to be approximately 16 dB greater at 4 than at 0.5 kHz. In conclusion, DPOAEs and TMCs may be used interchangeably to infer precise individual nonlinear cochlear characteristics at 4 kHz, but it remains unclear that the same applies to lower frequencies.