Vocal Fatigue in Mandarin-Speaking Teachers: Characteristics of Phonation and Resonance.

OBJECTIVE

To investigate phonatory and resonatory characteristics in Mandarin-speaking female teachers with vocal fatigue (VF).

METHODS

A case-control study was conducted among teachers in Shanghai, China. Participants included 18 vocal-fatigued teachers (VF), 17 non-vocal-fatigued teachers (NVF), and 16 nonoccupational voice users (NOVU). Subjective assessment included the Vocal Fatigue Index (VFI), Voice Handicap Index-10 (VHI-10), and GRBAS scale. Objective assessments included maximum phonation time (MPT), dysphonia severity index (DSI), fundamental frequency (F0), cepstral peak prominence, intensity, jitter, shimmer, harmonics-to-noise ratio (HNR), the rate, and regularity (jitter) of the laryngeal diadochokinesis (LDDK) (/ʔa/, /ha/, /ʔʌ/, /hʌ/). Articulatory features included vowel space area (VSA), formant centralization ratio (FCR), the formants (F1-F3), and their bandwidths (B1-B3). These measures were collected during vowels, passage reading, and free talking. A decision tree model was developed to identify key factors associated with VF.

RESULTS

Subjective voice assessments: the VF group showed significantly higher VHI-10 scores and grade (G) ratings of GRBAS compared with the NVF and NOVU (P < 0.05). Objective voice assessments: the VF had significantly lower DSI (P < 0.05), higher FCR, F1/i/, and F1/u/ (P < 0.05) than NVF and NOVU, and reduced MPT and VSA compared with the NVF (P < 0.05). F2/u/ was significantly higher in the VF than in the NVF (P < 0.05). Compared with the NOVU, the VF exhibited significantly higher jitter/i/, F2/a/, and B3/u/ (P < 0.05), as well as significantly lower HNR/u/, F2/i/, B3/i/, /ha/, and /hʌ/ rate (P < 0.05). Decision tree model: F2/u/, VHI-10, and DSI were identified as key discriminators of VF in teachers.

CONCLUSIONS

Teachers with VF demonstrate insufficient respiratory support, poor vocal quality, reduced LDDK ability, and limited articulatory movement range. F2/u/, VHI-10, and DSI play a crucial role in distinguishing VF.