Acoustic versus electronic modifications of hearing aid low-frequency output.

The rated quality and intelligibility of speech processed by hearing aids in which the low-frequency output had been reduced by either electronic modification (low-cut tone controls) or acoustic modification (vented or open earmolds) was investigated. Fifteen subjects with high-frequency hearing loss provided data for nine commercial hearing aids and both high and low background noise levels. Results for both background noise levels indicated that for hearing aids with a low-frequency cut off at or above 750 Hz (as measured in this investigation), the use of a vented or open earmold significantly improved both quality and intelligibility even when it had essentially no effect on the hearing aid's low-frequency output. The implication of the outcome is that for an individual with essentially normal low-frequency sensitivity and a high-frequency hearing loss, an earmold incorporating an opening should be used whenever possible, even though it may not be used for the purpose of controlling low-frequency amplification.