Simulations and Measurements of Human Middle Ear Vibrations Using Multi-Body Systems and Laser-Doppler Vibrometry with the Floating Mass Transducer.

Frank Böhnke,Theodor Bretan,Tobias Strenger,Stefan Lehner

doi:10.3390/ma6104675

Frank Böhnke, Theodor Bretan + Show 2 more

Open Access

https://doi.org/10.3390/ma6104675

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Abstract

The transfer characteristic of the human middle ear with an applied middle ear implant (floating mass transducer) is examined computationally with a Multi-body System approach and compared with experimental results. For this purpose, the geometry of the middle ear was reconstructed from μ-computer tomography slice data and prepared for a Multi-body System simulation. The transfer function of the floating mass transducer, which is the ratio of the input voltage and the generated force, is derived based on a physical context. The numerical results obtained with the Multi-body System approach are compared with experimental results by Laser Doppler measurements of the stapes footplate velocities of five different specimens. Although slightly differing anatomical structures were used for the calculation and the measurement, a high correspondence with respect to the course of stapes footplate displacement along the frequency was found. Notably, a notch at frequencies just below 1 kHz occurred. Additionally, phase courses of stapes footplate displacements were determined computationally if possible and compared with experimental results. The examinations were undertaken to quantify stapes footplate displacements in the clinical practice of middle ear implants and, also, to develop fitting strategies on a physical basis for hearing impaired patients aided with middle ear implants.

Highlights

The human middle ear (ME) is a mechanical structure that acts as a transducer to adapt the high acoustical impedance of the lymph of the inner ear to the low impedance of the surrounding air
Though all six ligaments of the middle ear were reconstructed, their geometries are not used in this study, and they are represented by Voigt elements of the Multi-body Systems (MBSs)
The maximum displacement calculated by the MBS method is 6 dB, according to 2 nm at f = 1 kHz

Summary

Introduction

The human middle ear (ME) is a mechanical structure that acts as a transducer to adapt the high acoustical impedance of the lymph of the inner ear to the low impedance of the surrounding air. In order to map the real dynamic mechanical behavior of the middle ear, an electromechanical analogy was used This approach is efficient, due to the simplification of a multi-degree of freedom system to a system with a strongly reduced number of variables, which could be evaluated by the limited computing power at that time. With this approach, it was difficult to examine the mechanical impact of the deficiency of ligaments or muscles on the displacement of the stapes footplate. Due to the high computational load, the ligaments could not be considered completely [2]

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