Choosing the optimal position of a vent microphone in acoustically open hearing systems - a numerical study
* Presenting author
Modern hearing systems are expected to offer various functionalities, e.g. aiding pathological hearing, in-ear monitoring, or providing augmented reality. This implies multiple simultaneous optimization targets for signal processing strategies, including sound pressure equalization together with feedback, noise and occlusion control. Ideally, the userexperience should match that of the open-ear scenario (acoustic transparency), plus specific enhancements. In order to approach all targets simultaneously, multiple in-ear microphones and drivers can be employed.In the current study, we investigate the problem of finding an optimal position for a “vent” microphone that is placed inside the venting tube of the hearing system. Specifically, the transfer function from this microphone to the ear drum in the occluded ear should be minimally dependent on the position of external sources, which is a prerequisite for various signal processing strategies. To this end, we used the Finite Element Method (FEM) to compute transfer functions from external sources to the vent microphone and to the ear drum. By exploiting the reciprocity principle, a large number of external source positions could be considered in one run. Both commercial and custom FEM implementations were used. The resulting optimal positions are discussed for different outer ear and ear canal anatomies.