Abstract:

Objectives: In this study, it was aimed to compare the effects of vowels on the intelligibility of Turkish monosyllabic speech materials in terms of their frequency content. Materials and Methods: The high-frequency energies of the speech materials comprised of monosyllable meaningful words in consonant-vowel-consonant format were filtered so that their filtered derivatives were generated. These materials and their derivatives were presented to normal-hearing young adults, and the intelligibility rates of each material were determined. The significance values of the high-frequency regions in the spectra of the materials in terms of intelligibility were calculated using their intelligibility rates obtained from different filter levels. All materials were grouped according to their vowel content, and the high-frequency significance values of the groups were compared statistically. Results: According to a one-way analysis of variance, there was a statistically significant difference between the vowel groups in terms of high-frequency significance scores. In the pairwise comparisons based on high-frequency significance values of the groups, there was no significant difference between the /ɑ/, /Ɔ/ and /u/ groups, but each differed from the /ɛ/, /i/ and /ɯ/ groups. On the other hand, the high-frequency significance values of the /y/ and /œ/ groups did not differ significantly from any group (vowels are transcribed with the International Phonetic Alphabet). Conclusion: According to the results of this study, it can be suggested to categorize /a/, /o/ and /u/ vowels as low-frequency, /y/ and /ɯ/ vowels as mid-frequency and /ɯ/, /i/ and /e/ as high-frequency vowels. This categorization may be used to make a more proper phonemic balance between lists, particularly in shortened versions of speech lists.

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