title: Viscoelastic properties of the human tympanic membrane studied with stroboscopic holography and finite element modeling.
abstract: A new anatomically-accurate Finite Element (FE) model of the tympanic membrane (TM) and malleus was combined with measurements of the sound-induced motion of the TM surface and the bony manubrium, in an isolated TM-malleus preparation. Using the results, we were able to address two issues related to how sound is coupled to the ossicular chain: (i) Estimate the viscous damping within the tympanic membrane itself, the presence of which may help smooth the broadband response of a potentially highly resonant TM, and (ii) Investigate the function of a peculiar feature of human middle-ear anatomy, the thin mucosal epithelial fold that couples the mid part of the human manubrium to the TM. Sound induced motions of the surface of ex vivo human eardrums and mallei were measured with stroboscopic holography, which yields maps of the amplitude and phase of the displacement of the entire membrane surface at selected frequencies. The results of these measurements were similar, but not identical to measurements made in intact ears. The holography measurements were complemented by laser-Doppler vibrometer measurements of sound-induced umbo velocity, which were made with fine-frequency resolution. Comparisons of these measurements to predictions from a new anatomically accurate FE model with varied membrane characteristics suggest the TM contains viscous elements, which provide relatively low damping, and that the epithelial fold that connects the central section of the human manubrium to the TM only loosely couples the TM to the manubrium. The laser-Doppler measurements in two preparations also suggested the presence of significant variation in the complex modulus of the TM between specimens. Some animations illustrating the model results are available at our website (www.uantwerp.be/en/rg/bimef/downloads/tympanic-membrane-motion).
authors.affiliation: Laboratory of Biomedical Physics, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium. Electronic address: daniel.degreef@uantwerpen.be.
authors.forename: Daniel
authors.initials: D
authors.lastname: De Greef
authors.affiliation: Laboratory of Biomedical Physics, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium; Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA; Department of Otology and Laryngology, Harvard Medical School, 243 Charles Street, Boston, MA 02114, USA.
authors.forename: Jef
authors.initials: J
authors.lastname: Aernouts
authors.affiliation: Laboratory of Biomedical Physics, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Aerts
authors.affiliation: Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA; Department of Otology and Laryngology, Harvard Medical School, 243 Charles Street, Boston, MA 02114, USA.
authors.forename: Jeffrey Tao
authors.initials: JT
authors.lastname: Cheng
authors.affiliation: Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA; Speech and Hearing Bioscience and Technology Program, MIT-Harvard Division of Health Sciences and Technology, 260 Longwood Avenue, Boston, MA 02115, USA.
authors.forename: Rachelle
authors.initials: R
authors.lastname: Horwitz
authors.affiliation: Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114, USA; Department of Otology and Laryngology, Harvard Medical School, 243 Charles Street, Boston, MA 02114, USA; Speech and Hearing Bioscience and Technology Program, MIT-Harvard Division of Health Sciences and Technology, 260 Longwood Avenue, Boston, MA 02115, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Rosowski
authors.affiliation: Laboratory of Biomedical Physics, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
authors.forename: Joris J J
authors.initials: JJ
authors.lastname: Dirckx
mesh_terms: D000161:Acoustic Stimulation; D004548:Elasticity; D020342:Finite Element Analysis; D006696:Holography; D006801:Humans; D008022:Ligaments / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D008307:Malleus / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D008954:Models, Biological; D049489:Stroboscopy; D014057:Tomography, X-Ray Computed; D014432:Tympanic Membrane / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D014783:Viscosity