Auditory filter shapes derived from forward and simultaneous masking at low frequencies: Implications for human cochlear tuning

Behavioral forward-masking thresholds with a spectrally notched-noise masker and a fixed low-level probe tone have been shown to provide accurate estimates of cochlear tuning. Estimates using simultaneous masking are similar but generally broader, presumably due to nonlinear cochlear suppression effects. So far, estimates with forward masking have been limited to frequencies of 1 kHz and above. This study used spectrally notched noise under forward and simultaneous masking to estimate frequency selectivity between 200 and 1000 Hz for young adult listeners with normal hearing. Estimates of filter tuning at 1000 Hz were in agreement with previous studies. Estimated tuning broadened below 1000 Hz, with the filter quality factor based on the equivalent rectangular bandwidth (Q_ERB) decreasing more rapidly with decreasing frequency than predicted by previous equations, in line with earlier predictions based on otoacoustic-emission latencies. Estimates from simultaneous masking remained broader than those from forward masking by approximately the same ratio. The new data provide a way to compare human cochlear tuning estimates with auditory-nerve tuning curves from other species across most of the auditory frequency range.