The final array design provides a directionality that amounts to an Articulation Index-weighted Directivity Index (AI-DI) of 8.5 dB. This is a substantial improvement over the 4-5 dB AI-DI typically reported for hearing aids. Moreover, directional hearing aids often roll off the low frequencies, because of the noise sensitivity issue. In contrast, the microphone array maintains full audibility throughout the range of speech frequencies.
The microphone array was tested with hearing-impaired listeners in the severe-to-profound segment, who are the most likely users of handheld assistive listening devices. The results showed that the measured AI-DI translated directly into an improvement in speech reception threshold.