Powerflow in arbitrary shaped memebranes: the human eardrum: how does sound energy travel in the human eardrum?

The eardrum and the ossicles of the middle ear function as an acoustic impedance transformer which passes sound energy in the air to the fluid of the inner ear. The eardrum is the first part of this chain and conveys sound energy in an extraordinary efficient way on to the middle ear ossicles. Up till now, the process of this energy conversion remains unknown. In recent literature it has been shown that that starting from measurements of the vibration of the surface of a plate it is possible to calculate how energy flows through the plate. With this so-called powerflow method it is possible to determine the location of energy sink and energy drain, but up till now the method has only been developed for application on flat plates of homogenous thickness. In the past two years the research group BIMEF has expanded the method to follow energy flow in a cylindrical curved plate, and now the method will be generalized to arbitrary curved plates and membranes. This requires a very complicated processing of the measured data. The recorded vibration data need to be transferred from the coordinate system of the object to a curvilinear coordinate system in which the powerflow calculations can be performed. Next, the powerflow data need to be back-traced to the coordinate system of the object. The realization of this generalized method will bring an important step forward in the applicability of the powerflow method, with applications is different fields of mechanics and acoustics. Simultaneously, a measurement setup will be developed to measure the shape and vibration of curved plates, using digital image correlation. With this setup vibrations will be measured of cylindrical and arbitrary shaped plates with known position of power source and drain so that the analysis method can be validate. Finally, the method will be expended to inhomogeneous membranes of varying thickness and arbitrary shape. Once this general method is realized, it will be applied to determine the acoustic-mechanical powerflow in the eardrum, so we can finally answer the question: how does sound energy flow in the eardrum?

Keywords:HEARING

Disciplines:Classical physics, Elementary particle and high energy physics, Other physical sciences, Biophysics