The effect of single-ossicle ear flexibility and eardrum cone orientation on quasi-static behavior of the chicken middle ear

Publication date: Available online 19 October 2018

Source: Hearing Research

Author(s): Pieter G.G. Muyshondt, Peter Aerts, Joris J.J. Dirckx

Abstract

In the single-ossicle ear of chickens, the quasi-static displacement of the umbo shows great asymmetry; umbo displacements are much larger for negative than for positive pressure in the middle ear, which is opposite to the typical asymmetry observed in mammal ears. To better understand this behavior, a finite-element model was created of the static response of the chicken middle ear. The role of flexibility of the extracolumella in the model was investigated, and the potential effect of the outward orientation of the tympanic-membrane cone was studied by building two adapted models with a flat and inverted membrane geometry. It was found that the extracolumella must be made of flexible material to explain the large inward displacements of the umbo, and that displacements of the footplate are much smaller due to bending of the flexible extracolumella. However, increasing extracolumellar stiffness mostly reduces umbo displacement rather than increasing footplate displacement. The results suggest that the inverted orientation of the membrane cone is responsible for the opposite asymmetry of the umbo displacement curve. The asymmetry of the footplate displacement was smaller, but increased towards positive middle-ear pressure in the case of a flat or inverted membrane geometry.

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