Consonant recognition loss in hearing impaired listeners

This paper presents a compact graphical method for comparing the performance of individual hearing impaired (HI) listeners with that of an average normal hearing (NH) listener on a consonant-by-consonant basis. This representation, named the consonant loss profile (CLP), characterizes the effect of a listener's hearing loss on each consonant over a range of performance. The CLP shows that the consonant loss, which is the signal-to-noise ratio (SNR) difference at equal NH and HI scores, is consonant-dependent and varies with the score. This variation in the consonant loss reveals that hearing loss renders some consonants unintelligible, while it reduces noise-robustness of some other consonants. The conventional SNR-loss metric Δ SNR₅₀, defined as the SNR difference at 50% recognition score, is insufficient to capture this variation. The Δ SNR₅₀ value is on average 12 dB lower when measured with sentences using standard clinical procedures than when measured with nonsense syllables. A listener with symmetric hearing loss may not have identical CLPs for both ears. Some consonant confusions by HI listeners are influenced by the high-frequency hearing loss even at a presentation level as high as 85 dB sound pressure level.