Psychophysical estimates of cochlear phase response: Masking by harmonic complexes

Jennifer J. Lentz, Marjorie R. Leek

Research output: Contribution to journalArticle

37 Scopus citations

Abstract

Harmonic complexes with identical component frequencies and amplitudes but different phase spectra may be differentially effective as maskers. Such harmonic waveforms, constructed with positive or negative Schroeder phases, have similar envelopes and identical long-term power spectra, but the positive Schroeder-phase waveform is typically a less effective masker than the negative Schroeder-phase waveform. These masking differences have been attributed to an interaction between the masker phase spectrum and the phase characteristic of the basilar membrane. To explore this relationship, the gradient of stimulus phase change across masker bandwidth was varied by systematically altering the Schroeder-phase algorithm. Observers detected a signal tone added in-phase to a single component of a masker whose frequencies ranged from 200 to 5000 Hz, with a fundamental frequency of 100 Hz. For signal frequencies of 1000-4000 Hz, differences in masking across the harmonic complexes could be as large as 5-10 dB for phase gradients changing by only 10%, The phase gradient that resulted in a minimum amount of masking varied with signal frequency, with low frequencies masked least effectively by stimuli with rapidly changing component phases and high frequencies masked by stimuli with more shallow phase gradients. A gammachirp filter was implemented to model these results, predicting the qualitative changes in curvature of the phase-by-frequency function estimated from the empirical data. In some cases, small modifications to the gammachirp filter produced better quantitative predictions of curvature changes across frequency, but this filter, as implemented here, was unable to accurately represent all the data.

Original languageEnglish (US)
Pages (from-to)408-422
Number of pages15
JournalJARO - Journal of the Association for Research in Otolaryngology
Volume2
Issue number4
DOIs
StatePublished - Dec 1 2001

Keywords

  • Auditory filters
  • Harmonic complexes
  • Masking
  • Phase

ASJC Scopus subject areas

  • Otorhinolaryngology
  • Sensory Systems

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