Modeling cochlear dynamics: Interrelation between cochlea mechanics and psychoacoustics

Abstract

A model of the cochlea was used to bridge the gap between model approaches commonly used to investigate phenomena related to otoacoustic emissions and more filter-based model approaches often used in psychoacoustics. In the present study, a nonlinear and active one-dimensional transmission line model was developed that accounts for several aspects of physiological data with a single fixed parameter set. The model shows plausible excitation patterns and an input-output function similar to the linear-compressive-linear function as hypothesized in psychoacoustics. The model shows realistic results in a two-tone suppression paradigm and a plausible growth function of the 2f(1)-f(2) component of distortion product otoacoustic emissions. Finestructure was found in simulated stimulus-frequency otoacoustic emissions (SFOAE) with realistic levels and rapid phase rotation. A plausible "threshold in quiet" including finestructure and spontaneous otoacoustic emissions (SOAE) could be simulated. It is further shown that psychoacoustical data of modulation detection near threshold can be explained by the mechanical dynamics of the modeled healthy cochlea. It is discussed that such a model can be used to investigate the representation of acoustic signals in healthy and impaired cochleae at this early stage of the auditory pathway for both, physiological as well as psychoacoustical paradigms.

Relation Between Cochlear Mechanics and Performance of Temporal Fine Structure-Based Tasks

“…Similarly to previous studies that simulated OAE in a transmission line model (Lineton and Lutman 2003;Choi et al 2008;Epp et al 2010;Verhulst et al 2012), the impedance irregularities along the BM were implemented by randomly varying the gain parameter, γ(x), across positions on the BM. A set of random numbers were samples from a normal distribution (standard variation = 0.01, mean = 0.9).…”

Spontaneous otoacoustic emissions in an active nonlinear cochlear model in the time domain

“…We extend a previously proposed frequency domain model [2] and put forward a spatially discrete, active nonlinear one-dimensional model of the cochlea in the time domain describing human SOAEs and their basic statistical distributions (for similar modeling approaches for mammalian cochleas, see [4,11,15]). Critical oscillators, i.e., oscillators at the critical point of the Hopf bifurcation, share essential properties with the cochlear amplifier residing in the hearing organs of mammals [1,3,9].…”

Input level dependence of distortion products generated by saturating feedback in a cochlear model

“…Transmission line models of the cochlea can predict DPs that arise from a dynamic interaction, including a saturating feedback [9][10][11]. However, clear explanations for DPs within the transmission line have not yet been reported because of the complex structure of the model [9] and the many parameters [10].…”

“…The simple models cannot explain the frequency ratio dependence because of the lack of a frequency term in the simple models described by Eqs. (11) and (12).…”

“…These phenomenological models can account for cochlear nonlinearities, as shown by the results obtained from the transmission line model [9][10][11].…”