Influence of a remote microphone on localization with hearing aids

When used with hearing aids (HA), the addition of a remote microphone (RM) may alter the spatial perception of the listener. First, the RM signal is presented diotically from the HAs. Second, the processing in the HA often delays the RM signal relative to the HA microphone signals. Finally, the level of the RM signal is independent of the distance from the RM to HA.

The present study investigated localization performance of 15 normal-hearing and 9 hearing-impaired listeners under conditions simulating the use of an RM with a behind the ear (BTE) HA. Minimum audible angle discrimination around an average angle of 45◦ was measured for three sets of relative gains and seven sets of relative delays for a total 21 conditions.

In addition, a condition with just the simulated BTE HA signals was tested. Overall, for both groups, minimum audible angle discrimination was best when the relative RM gain was small (−3 and −6 dB) and the delay was approximately 10-20 ms. Under these conditions, localization performance approached the level obtained in the BTE HA only condition.