The human cochlear mechanical nonlinearity inferred through the Schairer et al. (2003) model

  • Lance Nizami Independent Research Scholar, Palo Alto, California, USA


Schairer et al. (2003) hypothesized that a multiplicative internal sensory noise, combined with the cochlear mechanical nonlinearity, causes a probe’s detection threshold under forward- masking to systematically determine its psychometric function’s slope. Here, psychometric functions of unprecedented precision are shown for forward-masked probe-tone detection as a function of intensity of same-frequency forward-masker at fixed masker-probe time gap. Within the Schairer et al. model, these psychometric functions imply that the cochlear nonlinearity’s rate-of-change declines as a power function of dB SPL. Rates-of-change, once integrated, give the hypothetical nonlinearity itself, as a function of a single unknown parameter for which suitable values are inferred by comparing hypothetical rates-of-change in man to actual rates-of-change in animals. The model cochlear mechanical nonlinearity in man has similar magnitude and shape to those in animals.


Finney, D.J. (1971). Probit Analysis. London: Cambridge University Press.

Green, D.M. & Swets, J.A. (1988). Signal Detection Theory and Psychophysics. Los Altos, California, USA: Peninsula Publishing.

Nizami, L. (1999). On Auditory Dynamic Range. Doctoral dissertation, School of Graduate Studies, University of Toronto, Toronto, Ontario, Canada.

Rhode, W.S. & Recio, A. (2000). Study of mechanical motions in the basal region of the chinchilla cochlea. Journal of the Acoustical Society of America, 107, 3317-3332.

Schairer, K.S., Messersmith, J., & Jesteadt, W. (2008). Use of psychometric-function slopes for forward-masked tones to investigate cochlear nonlinearity. Journal of the Acoustical Society of America, 124, 2196-2215.

Schairer, K.S., Nizami, L., Reimer, J.F. & Jesteadt, W. (2003). Effects of peripheral nonlinearity on psychometric functions for forward-masked tones. Journal of the Acoustical Society of America, 113, 1560-1573.

Full Articles