Objective:
The use of distinct phonation types to create lexical meaning is a remarkable capability of the human voice. In the Jingpho language, this is exemplified by a vital contrast between modal and pressed vowels. However, a comprehensive, evidence-based understanding of its production mechanism is limited. Previous acoustic research is dated and lacks direct measures of glottal function. This study, therefore, aims to provide a detailed acoustic analysis of the modal/pressed vowel contrast in modern Jingpho, thus contributing to the broader scientific understanding of how controlled phonation types are produced.

Design:
Speech and electroglottography (EGG) data were collected from a 35-year-old male native Jingpho speaker. The corpus consisted of 460 monosyllabic words, covering all five pairs of modal and pressed vowels in Jingpho. Acoustic parameters, including Open Quotient (OQ), corrected H1-H2 (H1*-H2*), fundamental frequency (F0), and formants (F1, F2), were extracted and analyzed. Paired t-tests and Wilcoxon signed-rank tests were used to assess the statistical significance of the differences between modal and pressed vowels.

Results:
The results indicated that: (1) Modal vowels had a significantly higher OQ than their pressed counterparts (p<0.001), suggesting greater glottal constriction in pressed vowels. (2) H1*-H2* was generally higher for modal vowels, though the significance of this difference varied depending on the vowel and its temporal position within the syllable. (3) The relationship between F0 and the vowel contrast was tone-dependent: on the low-level tone (33), modal vowels had a higher F0, whereas on the low-falling tone (31), pressed vowels had a higher F0. (4) Formant analysis revealed that pressed vowels were generally produced with a more retracted tongue position (lower F2) compared to modal vowels.

Conclusions:
Compared to previous research, this study introduced OQ as a new parameter, providing a more direct measure of glottal states. our findings on spectral tilt (H1*-H2*) were consistent with Kong (2001), despite using a different calculation method. However, our conclusion on F0 differs with Kong (2001): we found that the relative F0 between modal and pressed vowels showed opposite patterns, in that pressed vowels had lower F0 on low-level tones but higher F0 on low-falling tones. This suggests that although statistically significant, F0 may not be a primary cue for the modal/pressed contrast in Jingpho. Also, tongue retraction was identified as a consistent pattern for pressed vowels.
In summary, from a speech production perspective, the Jingpho modal/pressed vowel contrast is fundamentally a phonation-type distinction. The parameters of OQ and H1*-H2* collectively reveal the differences in glottal characteristics, while formant analysis demonstrates that this phonatory opposition is consistently accompanied by an articulatory difference in tongue position.