Abstract
Temporal waveform characteristics differentially affect masking by harmonic complexes in birds and humans. In birds, complexes with relatively flat temporal envelopes are more effective maskers than complexes with highly modulated temporal envelopes. Flat temporal waveforms constructed using positive and negative Schroeder-phase algorithms result in large masking differences in humans, but little masking difference in birds. This effect may be related to differences in the cochlear phase characteristics in the two species. A psychophysical estimate of the phase characteristic has been reported in humans by finding the phase spectrum of a harmonic masker that produces the least masking. Here we estimated the phase characteristic for zebra finches using operant conditioning methods to measure masked thresholds for tones embedded in harmonic complexes with phases selected according to scaled modifications of the Schroeder algorithm. There was little difference between birds and humans when the scalar was between 0.0 and −1.0 (i.e., negative Schroeder phases), but humans showed less masking than birds when the scalar was positive. These results may reflect a more linear phase characteristic along the avian cochlea. [Work supported by NIH R01 DC00198 and NSRA DC00046.]
Published Version
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