Wim Soede par
ARDEA, Harmen Doumastraat 24, NL 2321 JL Leiden, The Netherlands
Mead C. Killion
Matthew J. Roberts
Etymotic Res., 61 Martin Lane, Elk Grove Village, IL 60007
Hearing-impaired listeners often have great difficulty understanding speech in surroundings with background noise or reverberation. Directional-microphone hearing aids can often reduce background noise in relation to the desired speech signal. To this end at the Delft University of Technology in The Netherlands, microphone systems were developed with strongly directional characteristics, using array techniques. Considerable attention was paid to optimization and stability. Free-field simulations of several robust models showed that a directivity index of 9 dB can be obtained. Simulations were verified with a laboratory model. The results of the measurements agreed well with the measurements, and based on these two, portable models were developed. The benefit of these microphone arrays for the hearing impaired was tested in a measurement setup with eight noise sources, simulating a true cocktail party. The results of the listening tests with 44 hearing-impaired subjects will be presented showing an average improvement of the S/N ratio of 7.0 dB for monaural fitting. The first results of research on another array type will be discussed.