The purpose of this study was to assess the relationship between the directivity of
a directional microphone hearing aid and listener performance. Hearing aids were fit
bilaterally to 19 subjects with sensorineural hearing loss, and five microphone conditions
were assessed: omnidirectional, cardioid, hypercardioid, supercardioid, and "monofit,"
wherein the left hearing aid was set to omnidirectional and the right hearing aid
to hypercardioid. Speech perception performance was assessed using the Hearing in
Noise Test (HINT) and the Connected Speech Test (CST). Subjects also assessed eight
domains of sound quality for three stimuli (speech in quiet, speech in noise, and
music). A diffuse soundfield system composed of eight loudspeakers forming the corners
of a cube was used to output the background noise for the speech perception tasks
and the three stimuli used for sound quality judgments. Results indicated that there
were no significant differences in the HINT or CST performance, or sound quality judgments,
across the four directional microphone conditions when tested in a diffuse field.
Of particular interest was the monofit condition: Performance on speech perception
tests was the same whether one or two directional microphones were used.
Key Words
Diffuse field - directional microphones - directivity index - hearing aids - monofit
- sound quality - speech perception
