Use of psychometric-function slopes for forward-masked tones to investigate cochlear nonlinearity.

Schairer et al. [(2003). "Effects of peripheral nonlinearity on psychometric functions for forward-masked tones," J. Acoust. Soc. Am. 133, 1560-1573] demonstrated that cochlear nonlinearity is reflected in psychometric-function (PF) slopes for 4 kHz forward-masked tones. The goals of the current study were to use PF slopes to compare the degree of compression between signal frequencies of 0.25 and 4 kHz in listeners with normal hearing (LNH), and between LNH and listeners with cochlear hearing loss (LHL). Forward-masked thresholds were estimated in LNH and LHL using on- and off-frequency maskers and 0.25 and 4 kHz signals in three experiments. PFs were reconstructed from adaptive-procedure data for each subject in each condition. Trends in PF slopes across conditions suggest comparable compression at 0.25 and 4 kHz, and potentially a wider bandwidth of compression in relative frequency at 0.25 kHz. This is consistent with other recent behavioral studies that revise earlier estimates of less compression at lower frequencies. The preliminary results in LHL demonstrate that PF slopes are abnormally steep at frequencies with HL, but are similar to those for LNH at frequencies with NH. Overall, the results are consistent with the notion that PF slopes reflect degree of cochlear nonlinearity and can be used as an additional measure of compression across frequency.