The Interaction Between Vowel Quality and Intensity in Loudness Perception of Short Vowels in Mongolian

This study investigated the influence of vowel quality on loudness perception and stress judgment in Mongolian, an agglutinative language with free word stress. We aimed to explore the effects of intrinsic vowel features, presentation order, and intensity conditions on loudness perception and stress assignment.

Eight Mongolian short vowel phonemes (/ɐ/, /ə/, /i/, /ɪ/, /ɔ/, /o/, /ʊ/, and /u/) were recorded by a native Mongolian speaker of the Urad subdialect (the Chahar dialect group) in Inner Mongolia. The short vowels were paired under different intensity conditions. Native Mongolian listeners from Inner Mongolia participated in two loudness perception experiments: Experiment 1 examined the effects of presentation order and different intensity conditions on loudness perception using pairs of vowels. Experiment 2 explored how different vowel pairs influence perceptual outcomes and identified specific thresholds and perceptual boundaries for loudness perception.

The findings revealed that intensity significantly affected loudness perception, modulated by vowel quality. Presentation order of vowels affected loudness perception, and vowel centralization and lip rounding play crucial roles as well. Central vowels, particularly /ə/, were perceived as more prominent, whereas rounded vowels were more likely to be judged as stressed under equated intensity conditions. The study also identified a perceptual tendency toward final prominence, influenced by sonority and vowel positioning.

This study highlights the intricate relationship among vowel quality, intensity, and stress perception in Mongolian. Different vowels exhibited distinct loudness perceptions at the same intensity level, emphasizing the importance of vowel quality in stress assignment. Vowels with higher sonority indices or those positioned peripherally in the vowel space are more likely to be perceived as prominent. These findings contribute to a broader understanding of the phonological processes and perceptual mechanisms in agglutinative languages and highlight the need for further research across diverse dialects.