Objective: To examine whether vocal characteristics estimated by acoustic parameters were associated with phlegm, yin deficiency, or cold-heat patterns.
Methods: A total of 75 college students (males:females = 53:22) aged 19-24 years were enrolled in this study. Each subject was asked to complete the phlegm pattern questionnaire (PPQ), yin deficiency questionnaire (YDQ) and cold-heat questionnaire (CHQ). For the acoustic analysis, each subject was asked to produce a sustained vowel sound (/a/) for 3 s to be used to calculate acoustic parameters. Then, habitual fundamental frequency (F0), jitter, shimmer, F0tremor, mean F0, standard deviation of F0, maximum F0, minimum F0, normalized noise energy, harmonic-to-noise ratio, signal-to-noise ratio, amplitude tremor, and power ratio were calculated using the Dr. Speech software. Finally, four hierarchical regression models with pattern questionnaire scores as dependent variables were formed to examine which factors among acoustic parameters, sex, and age were predictive of those pattern scores.
Results: PPQ, YDQ, heat, and cold pattern scores all formed significant regression model equations and the adjusted R2 values were 0.281, 0.164, 0.156, and 0.170, respectively. There were aging effects in the PPQ and YDQ models (standardized β=0.199, 0.271, respectively). Vocal tremor-related F0 tremor and vocal ringing-related power ratio parameters were associated with PPQ and YDQ scores. Gender was directly predictive of PPQ and indirectly moderated the relationship between power ratio and YDQ score. Vocal pitch-related habitual F0 and mean F0 were associated with heat and cold scores. These results indicate that the vocal qualities of phlegm- and yin deficiency-susceptible subjects tend to be ringing and less tremorous, and those of heat- and cold-susceptible subjects tend to be high-pitched.
Conclusion: Our study results suggest that vocal characteristics estimated by acoustic parameters are partially predictive of phlegm, yin deficiency, heat, and cold patterns. In terms of phlegm and yin deficiency patterns, there were direct or moderating effects of sex and age.