Deng, Delin

Purpose: Depression is prevalent yet frequently underdiagnosed. Although speech-based detection methods show promise, most prior studies have emphasized binary classification in nontonal languages. This study examined whether acoustic features of spontaneous Mandarin speech reflect depression as a categorical condition or a continuous, dimensional construct. Method: A validated emotional Mandarin speech corpus paired with self-reported depression severity scores was analyzed. Acoustic features were extracted using the extended Geneva Minimalistic Acoustic Parameter Set. A multistage analytic framework was applied, including random forest classification to distinguish depressed from nondepressed clips, linear mixed-effects modeling to examine group and severity effects, and unsupervised clustering to examine latent structure in the acoustic feature space. Results: The random forest classifier achieved an accuracy of 72.3% and an area under the receiver operating characteristic curve of 0.826 on the held-out test set. Model performance favored sensitivity over precision in identifying depressed clips. SHapley Additive exPlanations analysis identified features across multiple acoustic domains, including spectral, pitch-related, voice quality, cepstral, and intensity measures, as important contributors to model predictions. Among the Top 10 features, no acoustic features showed statistically significant group differences. In contrast, median and mean fundamental frequencies were significantly positively associated with depression severity. Clustering analysis revealed overlapping group structures and a continuous distribution of severity scores across clusters. Conclusions: These findings provide preliminary support for a dimensional conceptualization of depression in spontaneous Mandarin speech. While classification models can distinguish depressed from nondepressed speech with moderate accuracy, acoustic features appear to vary more consistently with symptom severity than with diagnostic group. Speech-based measures may therefore have potential for continuous monitoring of depression, although this possibility requires further longitudinal verification.

This study investigates how word-initial /l/ and /n/ are phonetically realized in Mandarin Chinese as produced by speakers from three regions: Beijing (close to Standard Mandarin), Changsha (where Xiang, which contains /l/ but not /n/, is also spoken locally), and Meizhou (where Hakka, which contains both /l/ and /n/, is also spoken locally), focusing on acoustic cue use and phonological context effects. Using acoustic analysis and random forest classification, we analyzed five acoustic measures (F2–F1 spacing, F3 frequency, BW1, ΔA1, and A1–P0) and evaluated their contribution to distinguishing the two sounds. Results showed that speakers from different regions used distinct cue weighting strategies: Beijing Mandarin speakers relied more on spectral cues, Meizhou Mandarin speakers showed greater reliance on nasality-related cues, and Changsha Mandarin speakers combined both, with greater variability. Phonological context, including preceding nasals and following vowels, further modulated cue realization in region-specific ways. These findings demonstrate how native phonological background and phonological environment shape the phonetic implementation of a shared Mandarin contrast and illustrate the value of combining acoustic and classification-based approaches for modeling gradient phonetic variation.