Cargando…

Cochlear impulse responses resolved into sets of gammatones: the case for beating of closely spaced local resonances

Gammatones have had a long history in auditory studies, and recent theoretical work suggests they may play an important role in cochlear mechanics as well. Following this lead, the present paper takes five examples of basilar membrane impulse responses and uses a curve-fitting algorithm to decompose...

Descripción completa

Detalles Bibliográficos
Autores principales: Bell, Andrew, Wit, Hero P.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: PeerJ Inc. 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6266938/
https://www.ncbi.nlm.nih.gov/pubmed/30515362
http://dx.doi.org/10.7717/peerj.6016
_version_ 1783375951411806208
author Bell, Andrew
Wit, Hero P.
author_facet Bell, Andrew
Wit, Hero P.
author_sort Bell, Andrew
collection PubMed
description Gammatones have had a long history in auditory studies, and recent theoretical work suggests they may play an important role in cochlear mechanics as well. Following this lead, the present paper takes five examples of basilar membrane impulse responses and uses a curve-fitting algorithm to decompose them into a number of discrete gammatones. The limits of this ‘sum of gammatones’ (SOG) method to accurately represent the impulse response waveforms were tested and it was found that at least two and up to six gammatones could be isolated from each example. Their frequencies were stable and largely independent of stimulus parameters. The gammatones typically formed a regular series in which the frequency ratio between successive members was about 1.1. Adding together the first few gammatones in a set produced beating-like waveforms which mimicked waxing and waning, and the instantaneous frequencies of the waveforms were also well reproduced, providing an explanation for frequency glides. Consideration was also given to the impulse response of a pair of elastically coupled masses—the basis of two-degree-of-freedom models comprised of coupled basilar and tectorial membranes—and the resulting waveform was similar to a pair of beating gammatones, perhaps explaining why the SOG method seems to work well in describing cochlear impulse responses. A major limitation of the SOG method is that it cannot distinguish a waveform resulting from an actual physical resonance from one derived from overfitting, but taken together the method points to the presence of a series of closely spaced local resonances in the cochlea.
format Online
Article
Text
id pubmed-6266938
institution National Center for Biotechnology Information
language English
publishDate 2018
publisher PeerJ Inc.
record_format MEDLINE/PubMed
spelling pubmed-62669382018-12-04 Cochlear impulse responses resolved into sets of gammatones: the case for beating of closely spaced local resonances Bell, Andrew Wit, Hero P. PeerJ Biophysics Gammatones have had a long history in auditory studies, and recent theoretical work suggests they may play an important role in cochlear mechanics as well. Following this lead, the present paper takes five examples of basilar membrane impulse responses and uses a curve-fitting algorithm to decompose them into a number of discrete gammatones. The limits of this ‘sum of gammatones’ (SOG) method to accurately represent the impulse response waveforms were tested and it was found that at least two and up to six gammatones could be isolated from each example. Their frequencies were stable and largely independent of stimulus parameters. The gammatones typically formed a regular series in which the frequency ratio between successive members was about 1.1. Adding together the first few gammatones in a set produced beating-like waveforms which mimicked waxing and waning, and the instantaneous frequencies of the waveforms were also well reproduced, providing an explanation for frequency glides. Consideration was also given to the impulse response of a pair of elastically coupled masses—the basis of two-degree-of-freedom models comprised of coupled basilar and tectorial membranes—and the resulting waveform was similar to a pair of beating gammatones, perhaps explaining why the SOG method seems to work well in describing cochlear impulse responses. A major limitation of the SOG method is that it cannot distinguish a waveform resulting from an actual physical resonance from one derived from overfitting, but taken together the method points to the presence of a series of closely spaced local resonances in the cochlea. PeerJ Inc. 2018-11-27 /pmc/articles/PMC6266938/ /pubmed/30515362 http://dx.doi.org/10.7717/peerj.6016 Text en © 2018 Bell and Wit http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited.
spellingShingle Biophysics
Bell, Andrew
Wit, Hero P.
Cochlear impulse responses resolved into sets of gammatones: the case for beating of closely spaced local resonances
title Cochlear impulse responses resolved into sets of gammatones: the case for beating of closely spaced local resonances
title_full Cochlear impulse responses resolved into sets of gammatones: the case for beating of closely spaced local resonances
title_fullStr Cochlear impulse responses resolved into sets of gammatones: the case for beating of closely spaced local resonances
title_full_unstemmed Cochlear impulse responses resolved into sets of gammatones: the case for beating of closely spaced local resonances
title_short Cochlear impulse responses resolved into sets of gammatones: the case for beating of closely spaced local resonances
title_sort cochlear impulse responses resolved into sets of gammatones: the case for beating of closely spaced local resonances
topic Biophysics
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6266938/
https://www.ncbi.nlm.nih.gov/pubmed/30515362
http://dx.doi.org/10.7717/peerj.6016
work_keys_str_mv AT bellandrew cochlearimpulseresponsesresolvedintosetsofgammatonesthecaseforbeatingofcloselyspacedlocalresonances
AT witherop cochlearimpulseresponsesresolvedintosetsofgammatonesthecaseforbeatingofcloselyspacedlocalresonances