Evaluation of loudspeaker-based spatial audio reproduction methods for hearing aid applications
Master Thesis of Vollmer, Lukas
Recent research has focused on the evaluation of hearing aids in virtual acoustic environments using spatial sound reproduction systems. The sound fields generated by these systems exhibit errors compared to the intended physical reference field, which are picked up by the hearing aid microphones. This leads to a potential decrease of hearing aid algorithm performance with audible artifacts.The investigations done so far have mainly considered the reproduction in anechoic rooms, including room acoustic effects by room acoustic modeling. For clinical applications, space limitations make anechoic rooms unavailable. Thus, reverberant rooms must be considered for the setup of spatial sound reproduction systems, the effect of which has not yet been investigated. In this thesis two spatial sound reproduction systems were tested with four spatial sound reproduction methods. The reproduction was simulated for two beamforming hearing aid algortihms for virtual sound source positions on a sphere around the head. The errors of the simulated ideal scenarios showed that the reproduction shows good results in terms of deviation from a reference transfer function of the ideal case. However, binaural parameters showed possibly perceptible errors for both investigated setups. To include the effects of the reproduction room, binaural loudspeaker transfer functions were measured and the virtual sources positions were tested again using these transfer function. The comparison of the results showed that the reproduction room further decreases the performance in terms of binaural parameters.