Basilar-membrane responses to multicomponent (Schroeder-phase) signals: Understanding intensity effects

Van Summers, Egbert De Boer, Alfred Nuttall

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Harmonic complexes comprised of the same spectral components in either positive-Schroeder (+Schr) or negative-Schroeder (-Schr) phase [see Schroeder, IEEE Trans. Inf. Theory 16, 85-89 (1970)] have identical long-term spectra and similar waveform envelopes. However, localized patterns of basilar-membrane (BM) excitation can be quite different in response to these two stimuli. Measurements in chinchillas showed more modulated (peakier) BM excitation for +Schr than -Schr complexes [Recio and Rhode, J. Acoust. Soc. Am. 108, 2281-2298 (2000)]. In the current study, laser velocimetry was used to examine BM responses at a location tuned to approximately 17 kHz in the basal turn of the guinea-pig cochlea, for +Schr and -Schr complexes with a 203-Hz fundamental frequency and including 101 equal-amplitude components from 2031 to 22 344 Hz. At 35-dB SPL, +Schr response waveforms showed greater amplitude modulation than -Schr responses. With increasing stimulation level, internal modulation decreased for both complexes. To understand the observed phenomena quantitatively, responses were predicted on the basis of a linearized model of the cochlea. Prediction was based on an "indirect impulse response" measured in the same animal. Response waveforms for Schroeder-phase signals were accurately predicted, provided that the level of the indirect impulse used in prediction closely matched the level of the Schroeder-phase stimulus. This result confirms that the underlying model, which originally was developed for noise stimuli, is valid for stimuli that produce completely different response waveforms. Moreover, it justifies explanation of cochlear filtering (i.e., differential treatment of different frequencies) in terms of a linear system.

Original languageEnglish (US)
Pages (from-to)294-306
Number of pages13
JournalJournal of the Acoustical Society of America
Volume114
Issue number1
DOIs
StatePublished - Jul 1 2003

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membranes
stimuli
waveforms
cochlea
impulses
guinea pigs
Membrane
linear systems
predictions
stimulation
excitation
animals
envelopes
harmonics
modulation
Stimulus
lasers
Prediction
Cochlea
Impulse

ASJC Scopus subject areas

  • Acoustics and Ultrasonics

Cite this

Basilar-membrane responses to multicomponent (Schroeder-phase) signals : Understanding intensity effects. / Summers, Van; De Boer, Egbert; Nuttall, Alfred.

In: Journal of the Acoustical Society of America, Vol. 114, No. 1, 01.07.2003, p. 294-306.

Research output: Contribution to journalArticle

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