Development of Phonemically Balanced Word List in Tamil for Speech Audiometry and Evaluation of Its Effectiveness in Adults

Speech audiometry has become an essential component of the audiological test battery. Various speech audiometry materials have been developed in different languages and also revised later to meet criteria such as familiarity of the words, phonetic/phonemic balance, number of test items, and dialectal variations. The current study focused on developing a PB word list in Tamil for adults. The study was carried out in two phases. Phase I involved the development of a PB word list in Tamil. Phase II included evaluating the effectiveness of the developed word lists on adults with normal hearing sensitivity and hearing impairment. A total of 500 bisyllabic words were used in creating a master list. The collected words were subjected to familiarity testing with 40 native Tamil speakers. From the master list of 500 words, 90% of the participants rated 320 words as most familiar, and those words were included in the study. The 320 words were validated by eight experts working in the fields of audiology, speech-language pathology, linguistics, and psychology. The disagreed-with words were excluded from the list, and only 270 words that were agreed upon by all the experts were included in the final list. The final lists comprised four-word lists with 25 phonetically balanced (PB) words per list. The final word lists were recorded and tested for goodness. These final words were then administered to find SIS scores for two groups. Group I consisted of adults with 120 normal hearing sensitivity, and Group II consisted of 130 adults with hearing impairment. The results were analysed using SPSS software. The mean SIS in adults with normal hearing sensitivity ranged from 99.4 to 99.8%. The SIS of adults with normal hearing sensitivity revealed no significant difference (p > .05) with respect to gender, ears, or across the four-word lists. All four-word lists provided similar scores, establishing the equivalency of word lists in individuals with normal hearing sensitivity as well as hearing impairment. A psychometric curve of performance intensity function in adults with normal hearing sensitivity revealed that the SIS score increased as the sensation level increased from 10 to 40 dB SL. There is a linear increase in SIS scores from 10 to 20 dB SL. A plateau was attained at 40 dB SL with 100% SIS scores. Thus, the present study recommends the use of 40 dB SL for SIS testing. Mean SIS scores for adults with mild, moderate, and severe hearing loss were found to be 90.1%, 65.4%, and 41.8%, respectively. A significant decrease in SIS was observed as the degree of hearing loss increased.