Advancements of phonetics in the 21st century: Phonetic universals, language variation, and phonetic grammar

This review, part of the journal’s special collection on Advancements of Phonetics in the 21st Century, examines the interplay between phonetic universals and language variation at both segmental and utterance levels. It traces the physiological and biomechanical foundations of phonetic universals established by 20th-century research while focusing on cross-linguistic variation explored predominantly in 21st-century research. Segmental phonetic universals include the role of the syllable in organizing segments and gestures, intrinsic vowel duration influenced by vowel height, extrinsic vowel duration due to coda voicing, intrinsic and co-intrinsic f0 variation affected by vowel height and onset consonant characteristics, respectively, and place effects on closure duration and VOT. While segmental universals stem from distinct mechanical bases, utterance-level universals emerge from respiratory and articulatory resets at utterance onset, shaping the entire speech production system—a perspective substantiated here based primarily on 21st-century phonetic research. These resets structure prosodic organization, leading to weakening effects at the right edge (e.g., f0 declination, articulatory declination, phrase-final lengthening) and strengthening effects at the left edge (e.g., domain-initial strengthening) and occasionally at the right edge as well (e.g., phrase-final strengthening) when sufficient time permits. Extensive evidence demonstrates that phonetic universals are further shaped by language-specific factors and the interaction between system-oriented and output-oriented constraints. This diversity calls for detailed phonetic descriptions tailored to each language, with phonetic grammar, as proposed here, fine-tuning phonetic realization accordingly. Research in the 21st century has also illuminated that segmental and utterance-level universals, traditionally regarded as distinct, are deeply interconnected, if not inseparable. The Extended Model of Phonetic Grammar is introduced as a framework for mediating this relationship within the phonetics-prosody interface as well as interactions with other higher-order linguistic structures. Furthermore, language variation within phonetic universals suggests that many phonetic processes, once considered automatic, are actively controlled by speakers, reflecting the unique evolutionary pathways of different languages.