In this study the occlusion effect was quantified for five types of earmolds with
different venting. Nine normal-hearing listeners and ten experienced hearing aid users
were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell
type earmolds with a novel vent design with equivalent cross-sectional vent areas,
and nonoccluding soft silicone eartips of a commercial hearing instrument. For all
venting systems, the occlusion effect was measured using a probe microphone system
and subjectively rated in test and retest sessions. The results for both normal-hearing
subjects and hearing aid users showed that the novel vents caused significantly less
occlusion than the traditional vents. Occlusion effect associated with the soft silicone
eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher
for the subjective occlusion rating than for the objectively measured occlusion. Perceived
occlusion revealed a closer relationship to measured occlusion in the ear in which
the measured occlusion effect was higher ("high OE" ear) than in the "low OE" ear.
As our results suggest that subjective judgment of occlusion is directly related to
the acoustic mass of the air column in the vent, the amount of perceived occlusion
may be predicted by the vent dimensions.
Key Words
Acoustic mass - earmold - hearing instruments - measured occlusion - novel venting
system - occlusion effect - perceived occlusion - prediction of occlusion effect
