Measuring very small mechanical impedances as in the human ear (vor Ort)
* Presenting author
Abstract:
The mechanical impedance is defined as the complex ratio of the dynamic force acting on a structure and the resulting velocity for a harmonic excitation. State-of-the-art measurements of mechanical impedances are based on jointly observing the applied force and the movement. This approach has limitations when the measured impedance is small, i.e., the total behavior is dominated by the impedance of the measurement probe rather than the structure under test. However, in hearing science especially the measurement of small impedances is of great interest, like in the middle and inner ear. Mechanical impedances of these structures are required, for example, for the development and verification of middle-ear implants or eardrum contact transducers.We here present an approach to measure very small impedances down to the order of magnitude of the human ear directly. The technique uses a standard impedance probe with an optimized measurement procedure, which allows to achieve very high SNRs and a high-accuracy compensation of the measurement probe. This results in measurable point impedances below 1 Ns/m across the whole audible frequency range, i.e., in the range of literature values of the human eardrum. The technique is evaluated based on the experimental characterization of several artificial mechanical loads.
