Christian Weistenhöfer

Determination of the Shape and Inertia Properties of the Human Auditory Ossicles

This paper describes a method to accurately determine the shape of the human middle ear ossicles. If the density and the shape of a body are known, the inertia properties can be calculated using commercially available software. The inertia properties have been calculated for the stapes and for the incudomalleal unit. Different rectangular views of the stapes and the incudomalleal unit are shown to depict the position of the center of gravity and the position of the principal axes of inertia.

Hearing aid and method for adjusting a hearing aid

The process of adapting a hearing aid to its wearer is to be simplified. To this end the acoustic conditions in the auditory canal, especially the acoustic impedance, are estimated by measuring the input impedance of the earpiece on the hearing aid. For adjusting the hearing aid it is worthwhile using the mechanical resonance of the system of hearing aid and auditory canal which can be detected with the aid of the input impedance. This is produced by a simplified equivalent circuit diagram from which the corresponding acoustic variables can be obtained.

Key Features of the Human Middle Ear

The human middle ear was investigated using a generalised circuit model which can simulate the spatial vibrations of the ossicular chain. The behaviour was observed for acoustic excitation via the normal air conduction path and for mechanic excitation due to shaking the complete temporal bone. More insight into the functionality of the middle ear was obtained by also considering abnormal conditions such as stiffenings. It turned out that the mammalian middle ear is superior to a columella ear due to its particular design. The placement of comparably heavy bones (malleus head and incus body) outside the main transmission path between the manubrium and the stapes footplate in combination with a very flexible ossicular chain creates several favourable properties.

Three‐dimensional measurements of a physical full‐size model of the human middle ear

Complete systematical investigations of the vibrational properties of the human middle ear are impossible to carry out by means of temporal bone measurements of a single specimen because of post‐mortem changes (time variance), damages to the object to be measured, and the irreversibility of manipulations. Measurements of physical models offer the facility for examining the properties of the human middle ear regardless of the above problems. The quality of the scientific findings obtained from the physical models depends on how good the properties of the real middle ear are reproduced by the elements, forms and materials chosen. A physical full‐size model of the human middle ear was developed that allows the use of measurement instrumentation which is applied for real ear measurements. One‐ and three‐dimensional measurements of the physical full‐size model will be presented. The quality of the model will be judged by comparisons with real ear measurements and model predictions. The fields of application of...