Improvement in aided sound localization with open earmolds: observations in people with high-frequency hearing loss.

Sound localization ability was tested in nine people with marked, bilateral, high-frequency hearing loss and little or no low-frequency loss. They had previously been fitted bilaterally with behind-the-ear hearing aids and closed earmolds and showed poorer aided than unaided localization performance. Further testing was conducted in unaided and aided conditions, with the aids coupled to closed, open, and "sleeve" (extra-open) earmolds. Closed earmolds affected localization, particularly in the frontal horizontal plane, but performance was restored to unaided levels in both of the open earmold conditions. In the lateral vertical plane, localization was found to correlate with the extent of difference between low- and high-frequency hearing levels. That result is discussed in terms of a dynamic, low-frequency localization cue. Open earmolds are argued to improve aided sound localization for the present sample by permitting undistorted access to low-frequency interaural time/phase differences.