[Impact of microphone position on sound localization in cochlear implant users]

The delivery of directional cues of a hearing device microphone are highly dependent on the position of the microphones. The aim of this work was the evaluation of different microphone positions with regard to the transmission of interaural time and level differences as well as the spectral characteristics and its impact on the localization abilities.

Head-related transfer functions of 30 subjects were measured with three different omnidirectional microphones at different positions: in the pinna (ITP), behind the ear (BTE), at the entrance of the ear canal (EEC). Sound localization abilities of 12 bilateral CI users was assessed for the microphone positions ITP and BTE.

Only the microphone positions in the ear (ITP, EEC) could sample the spectral cues of the pinna. However, the positioning of the microphone inside of the pinna did not significantly improve sound localization abilities compared to BTE microphones. For sound incidence from rear significantly less front-back confusions were achieved with the microphone inside of the pinna.

The microphone position in the pinna showed only a slight improvement in sound localization compared with BTE microphones in CI users. A precondition for better sound localization abilities is the improvement of the delivery of temporal and spectral fine structure cues in CI systems.