title: Finite-Element Modelling of the Response of the Gerbil Middle Ear to Sound.
abstract: We present a finite-element model of the gerbil middle ear that, using a set of baseline parameters based primarily on a priori estimates from the literature, generates responses that are comparable with responses we measured in vivo using multi-point vibrometry and with those measured by other groups. We investigated the similarity of numerous features (umbo, pars-flaccida and pars-tensa displacement magnitudes, the resonance frequency and break-up frequency, etc.) in the experimental responses with corresponding ones in the model responses, as opposed to simply computing frequency-by-frequency differences between experimental and model responses. The umbo response of the model is within the range of variability seen in the experimental data in terms of the low-frequency (i.e., well below the middle-ear resonance) magnitude and phase, the main resonance frequency and magnitude, and the roll-off slope and irregularities in the response above the resonance frequency, but is somewhat high for frequencies above the resonance frequency. At low frequencies, the ossicular axis of rotation of the model appears to correspond to the anatomical axis but the behaviour is more complex at high frequencies (i.e., above the pars-tensa break-up). The behaviour of the pars tensa in the model is similar to what is observed experimentally in terms of magnitudes, phases, the break-up frequency of the spatial vibration pattern, and the bandwidths of the high-frequency response features. A sensitivity analysis showed that the parameters that have the strongest effects on the model results are the Young's modulus, thickness and density of the pars tensa; the Young's modulus of the stapedial annular ligament; and the Young's modulus and density of the malleus. Displacements of the tympanic membrane and manubrium and the low-frequency displacement of the stapes did not show large changes when the material properties of the incus, stapes, incudomallear joint, incudostapedial joint, and posterior incudal ligament were changed by ±10 % from their values in the baseline parameter set.
authors.affiliation: Department of BioMedical Engineering, McGill University, 3775 rue University, Montréal, QC, H3A 2B4, Canada.
authors.forename: Nima
authors.initials: N
authors.lastname: Maftoon
authors.affiliation: Department of BioMedical Engineering, McGill University, 3775 rue University, Montréal, QC, H3A 2B4, Canada. robert.funnell@mcgill.ca.|Department of Otolaryngology-Head and Neck Surgery, McGill University, Montréal, QC, Canada. robert.funnell@mcgill.ca.
authors.forename: W Robert J
authors.initials: WR
authors.lastname: Funnell
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, McGill University, Montréal, QC, Canada.|Department of Pediatric Surgery, McGill University, Montréal, QC, Canada.
authors.forename: Sam J
authors.initials: SJ
authors.lastname: Daniel
authors.affiliation: Biomedical Physics, University of Antwerp, Antwerp, Belgium.
authors.forename: Willem F
authors.initials: WF
authors.lastname: Decraemer
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D004432:Ear, Middle / Q000502:physiology*; D020342:Finite Element Analysis; D005849:Gerbillinae; D013016:Sound
keywords: dynamic model; frequency response; ossicles; pars flaccida; pars tensa; sensitivity analysis; sound stimulus; tympanic membrane; vibration