Open Earmold Fittings for Improving Aided Auditory Localization for Sensorineural Hearing Losses with Good High-Frequency Hearing

Abstract

We tested the hypothesis that the use of nonoccluding earmolds for hearing aid fittings could optimize auditory localization in the vertical plane for people with moderate, low-frequency hearing losses and good hearing at frequencies above 4000 Hz. This benefit was expected to arise from leaving the pinna unobstructed and by optimizing hearing (unaided) for frequencies above the hearing aid's limit. Twenty-two participants had hearing losses greater than 30 dB over the range 250 to 2000 Hz and had minimal losses (< 30 dB) at 6000 Hz and 8000 Hz. Their auditory localization was tested, using a horizontal arc and a vertical arc of loudspeakers, when listening unaided and when fitted bilaterally with Behind The Ear hearing aids with three earmold types--closed (occluded), open (partly occluded), sleeve (nonoccluded). Localization of vertical plane sound sources was significantly poorer for the closed earmold condition than for unaided. The open and sleeve conditions were better than the closed condition, and, for the sleeve earmold, vertical localization was almost equal to that unaided. The capacity to benefit from using open rather than closed earmolds was related to hearing level; people with the best hearing at 4000, 6000, and 8000 Hz received the most benefit. There was limited evidence that open earmolds also can be advantageous for some aspects of horizontal plane localization. Nonoccluding earmolds optimize aided vertical localization for hearing aid users with good high-frequency hearing. The "sleeve" earmold, so far used only in research, may be a useful clinical option.