## 4 Results  
### Descriptive Analysis  
Detailed frequency distributions of the demographic and clinical variables--such as gender, smoking status, alcohol consumption, voice usage status, coffee intake, the presence of comorbidities, surgical history, and voice training status (including the number of training sessions)--are available in [26]. Figure 1 presents boxplots illustrating the changes in key acoustic parameters before and after voice therapy. In each panel, the light gray box represents the values prior to voice therapy, while the dark gray box indicates values following voice therapy. The F0 (Hz), which reflects the average rate of vocal fold vibration, showed no substantial difference between pre- and post-therapy conditions, with a similar distribution range observed. In contrast, jitter (%), representing cycle-to-cycle frequency variations, significantly decreased after therapy, suggesting improved vocal stability. A notable reduction was also observed in shimmer (%), which quantifies amplitude variability, indicatingenhanced consistency in voice amplitude post-therapy. Similarly, the NHR (dB), a measure of breathiness in the voice signal, was lower following therapy, implying an improvement in voice clarity and quality. The SFF (Hz), or the average frequency used during speech, remained relatively stable, with only a slight decreasing trend. Meanwhile, the MPT (s) increased after therapy, reflecting improved respiratory support and efficiency of phonation. Overall, these results indicate that voice therapy led to marked improvements in vocal stability and quality, particularly through reductions in perturbation measures (jitter and shimmer) and noise components (NHR), as well as an enhancement in sustained phonation ability (MPT). Figure 2 presents boxplots illustrating the changes in physical, emotional, and total scores before and after voice therapy. In each panel, the light gray box represents pre-therapy scores, while the dark gray box indicates post-therapy scores. Panel (a) displays the physical scores, which reflect functional aspects of the vocal mechanism and physical discomfort related to voice disorders. After therapy, there was a slight upward trend in these scores, suggesting that voice therapy may have contributed to improvements in vocal function and a reduction in physical strain associated with phonation. Although the increase was modest, it implies potential therapeutic benefits in the physical domain, warranting further statistical verification. Panel (b) shows the emotional scores, which assess the psychological and emotional burden caused by voice disorders, including anxiety, frustration, and social withdrawal. The post-therapy scores exhibited a more pronounced increase compared with the physical domain. This suggests that voice therapy had a notable positive impact on the emotional well-being of the participants. This improvement in emotional scores may be attributed to enhanced vocal function, leading to increased confidence in communication and reduced psychological distress. Panel (c) presents the  
Figure 1: Boxplots of acoustic parameters before and after voice therapy. The light gray boxes (left) represent pre-therapy values, while the dark gray boxes (right) represent post-therapy values. Each boxplot illustrates the distribution, median, and variability of the key acoustic measures, highlighting changes following voice therapy. total scores, which represent the combined impact across both the physical and emotional domains. A significant increase in total scores was observed after therapy, indicating a comprehensive improvement in voice-related quality of life. The changes in score distributions, as visualized through the boxplots, reinforce the therapeutic effect not only on the objective functional measures but also on the patients' subjective experiences and perceptions. In summary, the results suggest that voice therapy provides multidimensional benefits.