# Speech Enhancement Algorithms: A Systematic Literature Review
## 3 Method
### Quality Assessment (QA) Rules  
In any systematic literature review, applying Quality Assessment (QA) rules is considered the last step in identifying the final list of candidate papers for inclusion. QA rules were applied to evaluate the quality of the research papers in accordance with the set research questions. Given the lack of standard empirically grounded QA rules suitable for use in such study designs, we implemented a scoring system to evaluate the quality of the papers eligible for inclusion in our systematic review based on the rules provided in [50]. Following the study selection process, we applied eight additional criteria in order to improve the results. QA rules were applied to each nominated paper in order to assess the quality of its contents and select only those studies most relevant to our SEA topic. Using the procedure suggested in [47], we checked the quality of each candidate paper for inclusion based on the following QA checklist:  
1. Are the research objectives clearly stated? 2. Does the article introduce new techniques or contributions to the field of SEA? 3. Is there enough background information in the paper? 4. Is the methodology used in the research clearly described? 5. Does the paper contain answers to the research questions? 6. Are research results reported? 7. Are the limitations of the study addressed effectively? 8. Overall, is the paper considered useful? Each question had three possible answers, with points being scored in the following way:  
1. The study was marked with \"Yes\" if the answer to the QA item was positive, where \"Yes\" = 1. 2. The study was marked with \"No\" if the answer to the QA item negative, where \"No\" = 0. 3. The study was marked with \"Partial\" if it only partially answered the QA item, where \"Partial\" = 0.5. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline
**Inclusion Criteria** & **Exclusion Criteria** \\ \hline Papers that are relevant to the topic of SEA. & Papers that are not relevant to the topic of SEA. \\ \hline Papers published during the period 2015–2024 & Papers published before 2015. \\ \hline Scientific journals or conference papers. & Papers that were not submitted to scientific journals or conferences. \\ \hline Papers written in English language & Papers written in a language other than English. \\ \hline Papers answering one or more of the research questions. & Papers that did not answer any of the research questions. \\ \hline Papers that were more than three pages and that were not duplicates. & Papers that were duplicate papers or not available. \\ \hline \end{tabular}
\end{table} 
Table 3: Criteria used in the exclusion and inclusion stage. The procedure for quality assessment is illustrated in Figure 4. The QA score of the research studies was achieved by weighing their quality alongside the QA questions; a paper was selected if it had a quality score equal to or greater than four. The results are presented in Table 4. Then, for each research study, the total score was computed based on a predefined threshold. If the total score was grater than or equal to four, the candidate study was included; on the other hand, if the score was less than four, the candidate study was excluded. Based on this procedure, three studies were excluded after implementing the quality assessment. In the QA procedure, studies were scored based on the degree to which specific criteria were met. The steps are summarized as follows. First, the questions used for the assessment procedure were defined. A scale was then determined to assign ranks to the papers based on the list of quality assessment questions. The total score value was obtained after summing all the weights provided based on these questions. Afterwards, a threshold of four was set, with papers excluded if this threshold was not med. On this basis, three papers were excluded. The final number of retained studies was 47.