Growth of forward masking was measured to determine the relative rate of basilar-membrane (BM) response growth at the characteristic-frequency (CF) place that was stimulated with a higher-frequency tone. Two signal frequencies (fs) were used, 1 kHz and 4 kHz. The masker frequency was 1.1 or 1.2fs. A lower-frequency masker (0.6fs) was also used to replicate previously published data. Previous data obtained using a method for deriving the BM input-output function based on temporal masking curves suggested a linear growth of the BM response to a tone with a frequency equal or higher than 1.1fs and a compressive growth for the CF tone. This study demonstrates that the growth-of-masking method for deriving the BM response provides a similar result (indicating a compressive growth for the CF tone) when a low-frequency masker is used but leads to a fundamentally different result indicating an expansive response growth when a higher-frequency masker is used. The expansive growth is observed even when a low-pass noise is used to limit potential off-frequency listening. The data will be related to mechanical BM data and the equivalence of the two psychophysical methods for deriving BM compression will be discussed [Supported by NIH grants DC00683 and DC006804].

       Wojtczak, M. and Viemeister, N.F. (2006). Estimating the rate of response growth using above characteristic-frequency maskers. Presented at the 151st Meeting of the Acoustical Society of America.

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