Normative Formant Data for Korean Vowels: A Resource for Clinical and Pedagogical Application

Objectives: This study aims to establish large-scale normative data for vowel formant frequencies and speech intelligibility (SI) in healthy Korean adults, providing a critical resource for clinical and pedagogical applications in speech-language pathology and voice science.Methods: A comprehensive cross-sectional analysis of 4,235 healthy Korean adults across three distinct age groups was conducted. We systematically measured multiple acoustic variables including F1, F2, vowel space areas (VSA_3, VSA_4, VSA_5), Vowel Articulation Index, Formant Centralization Ratio, and F2 ratio using customized Praat scripts, and assessed subjective SI through perceptual measures to establish reliable baseline data.Results: Significant age-related differences were found in all variables except the F2 ratio (p=.14). Significant sex-based differences were confirmed for all variables except the F1 of /o/ (p=.327). All acoustic metrics correlated significantly with SI, with VSA_5 demonstrating the highest correlation among all vowel space metrics (r=-.56, p<.01), suggesting its potential clinical utility as a complementary objective measure for speech assessment.Conclusion: This study provides robust, large-scale normative data confirming that age and sex significantly influence Korean vowel acoustics, with older age groups showing notable reductions in VSA and SI. Among the acoustic metrics examined, VSA_5 showed the strongest correlation with perceived speech intelligibility, indicating its potential as a meaningful objective complement to subjective SI assessment. These findings may offer a practical reference for clinicians in voice assessment, differential diagnosis, and monitoring rehabilitation progress in individuals with speech and voice disorders.