Relating Sound Externalization, Own-Voice Perception, and Occlusion in Adults With Hearing Aids

A recent study found that hearing aids fitted with highly occluding domes had an impact on the perception of externally presented speech, producing sound images that were perceived as too close or even inside the head. The present study examined whether this phenomenon is related to the well-known occlusion effect, which describes changes in ear canal levels and perceived own-voice quality during speaking.

Participants were 10 young adults with normal hearing and 10 young adults with sensorineural hearing loss. All participants were fitted with both closed- and open-fit hearing aids, and hearing aid users were also tested with their own devices. Externalization was measured using a numerical scale from 0 (inside the head) to 10 (at the loudspeaker). Participants also rated the naturalness of their own voice while speaking using a subjective scale from 1 (most unnatural) to 10 (most natural). Occlusion was also measured objectively for open and closed fittings using real ear measurements.

Externalization ratings were significantly higher for unaided than aided listening and for open versus closed domes. Similarly, own-voice ratings tended to be higher for unaided versus aided listening and for open versus closed domes. Although these broad patterns suggest that reduced ratings are associated with more occlusion, objective measures of occlusion did not account for a significant amount of the variance in either kind of rating. Similarly, individual own-voice ratings did not significantly predict individual externalization ratings. The data obtained with hearing aid users wearing their own devices suggested that regularly worn devices can have positive effects on own-voice perception while disrupting externalization.

Overall, compared with unaided listening, hearing aids negatively affected externalization and own-voice perception, with larger effects for closed than open fittings. However, at the individual level, measures of occlusion and sound externalization were not strongly related.