# Acoustic Voice Analysis as a Tool for Assessing Nasal Obstruction: A Systematic Review
## 2 Materials and Methods
### Quality Assessment  
We used a modified Downs and Black checklist to assess the methodological quality of the included studies [29]. This checklist encompasses 27 criteria that comprehensively address the areas of reporting, external and internal validity, and power. The original Downs and Black checklist is evaluated on a scale of 32. A two-point rating system is used for all items, with the exception of items 5 and 27. The categorization of \"yes\" is worth one point, whereas \"no\" or \"unable to determine\" is worth zero points. The rating for item 5, which evaluates the description of confounders, is two points; \"yes\" receives two points, \"partial description\" receives one, and \"no\" receives zero. The original score for item 27 was five points, which pertains to the statistical efficacy of the sample size. For the objectives of this review, item 27 was modified to be scored as '1' if power was reported, and '0' if not. Only 19 of the Downs and Black Checklist's questions are completely relevant to observational research, while eight of them are exclusive to randomized controlled trials (questions 4, 8, 13, 14, 15, 19, 23, and 24), as the other studies have pointed out [30; 31]. We therefore used a modified Downs and Black Checklist, excluding the aforementioned items. The final version used for the present study included, therefore, 19 items with a maximum score of 20 points.  
\begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline
**Reference** & [18] & [19] & [20] & [21] & [22] & [23] & [24] & [25] & [26] & [27] \\ \hline \multicolumn{8}{c}{_Nasal Obstruction Measurements_} \\ \hline Nasometer & & ✓ & ✓ & & & ✓ & & & \\ MCA & & & & ✓ & & ✓ & & \\ MCV & & & & & ✓ & & & \\ TNV & & & & ✓ & & & & \\ TNR & & & ✓ & ✓ & & & & ✓ \\ NOSE & & & & ✓ & ✓ & & ✓ & & \\ Nasal Polyp Score & § & & & & & & & & \\ Lund–Mackay & \(\dagger\) & \(\dagger\) & & & & & & & \\ \hline \multicolumn{8}{c}{_Acoustic Voice Analysis_} \\ \hline Jitter & & \(\times\) & \(\times\) & ✓ & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) \\ Shimmer & & \(\times\) & \(\times\) & ✓ & ✓ & ✓\(\dagger\) & \(\times\) & \(\times\) & \(\times\) \\ F0 & & \(\times\) & \(\times\) & ✓ & \(\times\) & \(\times\) & ✓\(\dagger\) & \(\times\) & \(\times\) \\ F1 & & & & & & \(\times\) & & & \(\times\) \\ F2 & & & & & & \(\times\) & & & \(\times\) \\ F3 & & & & & & \(\times\) & & & \(\times\) \\ F4 & & & & & & \(\times\) & & & \(\times\) \\ NHR & & & \(\times\) & \(\times\) & ✓ & & \(\times\) & & \(\times\) \\ HNR & & & & ✓ & & & & & \\ VTI & & & & ✓ & & & & & \\ SPI & & & & ✓ & & & & & \\ DUV & & & & ✓ & & & & & \\ DVB & & & & ✓ & & & & & \\ vAm & & & & ✓ & & & & & \\ LTAS & ✓ & & & & & & & & \\ VOT & & & & & & & & \(\times\) & \\ \hline \hline \multicolumn{8}{c}{_Subjective Voice Assessment_} \\ \hline GIRBAS & & \(\times\) & & & & & & & \\ VAS & ✓ & & & & & ✓ & & \\ VHI & & & & & & ✓ & & \\ PROM for voice change & & & & & & & & & \\ \hline \hline \end{tabular} \(\prime\): Significant change, \(\times\): No significant change, §: Descriptive findings without statistical test, ✓: Significant change only in a subgroup, \(\dagger\): No post-op score. *: 61% no change, 36% favorable change, 3% worsening.  
\end{table}
Table 3: Nasal obstruction and voice assessment parameters with reported significance in different studies.  
Two independent reviewers performed the evaluation. All discrepancies were resolved through discussion and consensus. The overall score of each study was transformed into a percentage by dividing its raw score by 20 and then multiplying the result by 100 to enable a quality grading of the studies. [PERSON]'s ranking system was then used to classify the overall critical appraisal percentage as either \"good,\" \"fair,\" or \"poor\" quality [32]. We utilized [PERSON]'s model to classify papers with critical appraisal scores of 71% or higher as good quality, 54-70% as fair quality, and 53% or less as poor quality when applied to the modified Downs and Black scoring system.