Revised estimates of human cochlear tuning from otoacoustic and behavioral measurements

TLDR

Human cochlear tuning at frequencies above 1 kHz has been inadequately characterized, with prior noninvasive methods relying on masking or suppression. The authors aim to develop an objective, noninvasive method to determine cochlear frequency selectivity at low and moderate sound levels. Their method measures stimulus‑frequency otoacoustic emissions in humans, avoiding reliance on masking or suppression. Otoacoustic and new behavioral data reveal that human cochlear tuning at low levels is more than twice as sharp as behavioral studies suggest, differs in frequency dependence, is sharper than in cat and guinea pig, and may enhance speech communication.

Abstract

We develop an objective, noninvasive method for determining the frequency selectivity of cochlear tuning at low and moderate sound levels. Applicable in humans at frequencies of 1 kHz and above, the method is based on the measurement of stimulus-frequency otoacoustic emissions and, unlike previous noninvasive physiological methods, does not depend on the frequency selectivity of masking or suppression. The otoacoustic measurements indicate that at low sound levels human cochlear tuning is more than twice as sharp as implied by standard behavioral studies and has a different dependence on frequency. New behavioral measurements designed to minimize the influence of nonlinear effects such as suppression agree with the emission-based values. A comparison of cochlear tuning in cat, guinea pig, and human indicates that, contrary to common belief, tuning in the human cochlea is considerably sharper than that found in the other mammals. The sharper tuning may facilitate human speech communication.