Externalization of speech through hearing aids differing in microphone position and dome type

An experiment was conducted to examine how different hearing aid styles affect the externalization of speech. Of particular interest were effects of microphone position (behind-the-ear versus in-the-canal) and dome type (closed versus open). Participants were young adults with and without hearing loss, who were fitted with hearing aids that allowed variations in the microphone position and the dome type. They were seated in a large sound-treated booth and presented with monosyllabic words from loudspeakers at a distance of 1.5 m. Their task was to rate the perceived externalization of each word using a rating scale that ranged from 10 (at the loudspeaker in front) to 0 (in-the-head) to −10 (behind the listener). We observed a large intersubject variability in ratings. On average, compared to unaided listening, hearing aids tended to reduce perceived distance and lead to more in-the-head responses. This was especially true for closed domes in combination with behind-the-ear microphones. We also observed a strong association between poor externalization and front-back confusions.