Speaker
Description
When wearing hearing aids, a mechanical interaction between the earmould and the skin of the outer ear canal occurs. The extent of this interaction, its influence on wearing comfort and long-term effects caused by continuously wearing a hearing aid are largely unknown. To quantify this interaction we develop a measurement system to measure the mechanical point impedance inside the human ear canal. The measurement system consists of an acceleration sensor and a vibration exciter that are both mounted on a cantilever beam. An electromechanically motivated model is used to estimate the attached mechanical load impedance. Because the model neglects torsional motion, a finite‑element (FE) model of the device was used to evaluate the induced rotational velocity for ideal and misaligned sensor/actuator placements. Furthermore, a tuning‑fork‑shaped beam was investigated in the simulation as a means to suppress torsional components. The FE analysis shows that the tuning‑fork geometry reduces rotational velocity compared to a conventional rectangular beam. Prototypes incorporating the new beam were subsequently built and analyzed using Laser-Doppler-Vibrometry, indicating a modest reduction in torsional motion for the new design.