Adult hearing-aid users with cochlear dead regions restricted to high frequencies: Implications for amplification.

Objectives: Cochlear dead regions (DR) are common in adult hearing-aid users, but are usually restricted to high frequencies. The aim was to determine the benefit of high-frequency amplification for ears with and without high-frequency DRs.

Design: Participants were fitted with the study hearing aid and tested under four conditions: unfiltered (NAL-NL2 prescription), and low-pass filtered at 1.5, 2, and 3 kHz. VCV stimuli were presented at 65 dB (A) in quiet and in 20-talker babble at a signal-to-babble ratio of 0 dB.

Study Sample: Experienced adult hearing-aid users: one group of 18 with a DR edge frequency above 1.5 kHz, and a group of 18 matched controls.

Results: Overall performance was best in the unfiltered condition. There was no significant difference in mean performance between the two groups when tested in quiet. However, the DR group obtained less benefit from high-frequency amplification when tested in babble: the mean difference between the unfiltered and 3-kHz filtered condition was 6% and 13% for the DR group and controls, respectively.

Conclusions: In adults with a moderate hearing loss and a restricted DR, speech recognition was always best in the unfiltered condition, although mean performance in babble was lower for the DR group.