Lexical tone perception in Thai normal-hearing adults and those using hearing aids: a case study

Lexical tone perception in Thai adults with normal hearing and those with sensorineural hearing-loss using hearing aids was investigated to evaluate the benefit of using hearing aids for tone perception. Tone perception pattern across groups was also compared. Identification tests (with white noise and clean conditions) using a two alternative forced choice task were carried out to systematically compare confusion pattern in each tonal pair. Average percent correct responses, balanced confusion matrices, and signal detection theory (SDT) bias values of c for confusable tone pairs were obtained. Overall, the results showed that there seem to be no significant gain in the tone perception of Thai hearing-impaired adults with hearing devices. Tonal confusion patterns differ across groups. Specifically, out of 10 tone pairings, average bias values of c showed that normal hearing adults favor specific members in 6 tone pairs (i.e., the first member of the following: mid-falling, mid-rising, low-falling, low-high, falling-high, and risinghigh). Interestingly, for hearing-impaired adults (with and without hearing devices), reverse pattern, favoring the second member of those pairs, was found.