Consonant-vowel intensity ratios for maximizing consonant recognition by hearing-impaired listeners

The effect of adjusting the consonant-vowel (C-V) intensity ratio on consonant recognition in 18 subjects with sensorineural hearing impairment was investigated. C-V intensity ratios in a set of 48 vowel-consonant nonsense syllables were adjusted in steps of 3-6 dB depending on the subject's dynamic range of hearing. An increase in consonant intensity is referred to here as consonant enhancement (CE). The value of CE producing the highest consonant recognition score (CRmax) is defined as CEmax. Both CEmax and CRmax were determined for each subject for each of the 48 nonsense syllables. Consonant type was found to have a highly significant effect on CRmax, the gain in consonant recognition, and CEmax. The effect of vowel environment was also significant, but of much smaller magnitude. Audiogram configuration was found to have a small effect and was only significant for CRmax. The results of the study also showed that individualized adjustment of the C-V intensity ratio for each subject and consonant-vowel combination can produce substantial improvements in consonant recognition. These data can be used to estimate upper bounds of performance that, in principle, can be obtained by appropriate adjustment of the C-V intensity ratio.