Limiting High-Frequency Hearing Aid Gain in Listeners with and without Suspected Cochlear Dead Regions

The purpose of this study was to compare threshold-matched ears with and without suspected cochlear dead regions in terms of the speech perception benefit from high-frequency amplification. The Threshold Equalizing Noise Test (TEN) was used to assess the presence of dead regions. Speech perception was measured while participants were wearing a hearing aid fit to approximate DSL[i/o] targets. Consonant identification of nonsense vowelconsonant-vowel combinations was measured in quiet using a forced-choice procedure. Phoneme recognition was measured at signal-to-noise ratios ranging from 0 to +15 dB using the Computer-Assisted Speech Perception Assessment test (CASPA). Recognition scores were obtained for unfiltered stimuli and stimuli that were low-pass filtered at the estimated boundary of the suspected dead regions, ½ octave above and 1 octave above the boundary. Filter settings for the ears without suspected dead regions were the same as settings of the threshold-matched counterpart.

In quiet and in low levels of noise, speech perception scores were significantly higher for the wide-band (unfiltered) condition than for the filtered conditions, and performance was similar for the ears with and without suspected dead regions. In high levels of noise, mean scores were highest in the wide-band condition for the ears without suspected dead regions, but performance reached an asymptote for the ears with suspected dead regions. These results suggest that patients with cochlear dead regions may experience speech perception benefit from wide-band high-frequency gain in quiet and low levels of noise, but not in high levels of noise.

Key Words

Cochlear dead regions - hearing amplification - speech perception