## 3 Materials and Methods
### K-VRQOL Questionnaires  
Subjective voice evaluations commonly utilize tools such as the Voice Handicap Index (VHI) and the V-RQOL questionnaire. In particular, the close relationship between health and quality of life highlights the importance of evaluating voice-related quality of life, as such assessments can capture the perceived impact of voice disorders across the personal, social, and occupational domains [26; 27; 28]. [PERSON] et al. [11] translated the V-RQOL into Korean and validated the Korean version (K-VRQOL) with both individuals with voice disorders and the general adult population. Their study found that the item discrimination indices were statistically significant, and strong correlations were observed among individual items. Furthermore, the K-VRQOL scores were significantly higher among healthy adults compared with those with voice disorders, indicating that individuals with voice disorders experience greater discomfort and reduced quality of life due to their vocal problems.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Number of samples** & 63 female and 35 male voices \\
**Average age** & 51 \\  & vocal fold polyp (31), vocal paresis (3), vocal nodule (19), mutational \\  & dysphonia (1), thyroid nodule (1), hoarseness (4), muscle tension \\
**Types of voice disorders (numbers)** & dysphonia (7), sulcus vocalis (2), presbyphonia (8), dysphonia (10), vocal \\  & cord cyst (9), leukoplakia (2), thyroid cancer (2), vallecular cyst (1), vocal \\  & mass (2), and laryngopharyngeal reflux (1). \\  & gender, smoking status, alcohol status, voice user status, coffee status, \\  & comorbidity, surgery status, voice training status, the number of training sessions, and acoustic parameters measured before and after voice \\  & disorder therapy such as F0 (Hz), jitter (\%), shimmer (\%), NHR (dB), SFF (Hz), and MPT (s). \\ \hline \hline \end{tabular}
\end{table}
Table 1: Overview of the dataset utilized in this study.  
Based on these findings, the K-VRQOL was suggested as a useful tool for evaluating voice-related quality of life. It is concise and easy to administer, making it practical not only for assessment purposes but also for guiding therapy planning and monitoring therapeutic outcomes.  
The V-RQOL is a subjective assessment tool developed by [PERSON] and [PERSON] [29]. In this study, the Korean adaptation of the V-RQOL by [PERSON] et al. [11], known as the K-VRQOL, was used. Among its 10 items, the 10 th item was modified to read, \"I have become less outgoing (because of my voice)\". The K-VRQOL is a useful tool for evaluating the impact of voice disorders on an individual's quality of life. It consists of two subdomains: emotional and physical. The variables associated with the emotional domain are items 4, 5, 8, and 10, whereas those associated with the physical domain are items 1, 2, 3, 6, 7, and 9. Responses are recorded on a 5-point Likert scale, where 1 indicates \"no problem\", 2 \"a slight problem\", 3 \"a moderate problem\", 4 \"a severe problem\", and 5 \"as bad as it can be\". The raw scores range from 0 to 50 and are converted to standardized scores ranging from 0 to 100. A lower standardized score indicates a poorer voice-related quality of life, while a higher score reflects a minimal or no impact of voice problems on quality of life [9; 11]. The details are provided in Table 2.