# Acoustic Voice Analysis as a Tool for Assessing Nasal Obstruction: A Systematic Review
## 6 Conclusions  
This systematic review provides an in-depth analysis of the application of voice analysis as a tool for assessing nasal obstruction, with particular attention given to acoustic parameters and their correlation with objective and subjective measures of obstruction. The results indicate that, although acoustic voice analysis represents a potential tool for assessing nasal obstruction and hyponasality, available evidence remains limited. Currently, most studies focus on evaluating glottic sound alterations and dysphonia, rather than the effects that the vocal tract, including nasal cavities, may have on voice production. This highlights the need for further research to develop more advanced algorithms and validate standardized protocols for voice analysis in nasal obstruction assessment. Concerning the relationship between acoustic analysis parameters and nasal obstruction, the present research found that the shimmer parameter was the one that changedthe most in cases of nasal obstruction and exhibited significant changes in the majority of studies (3 studies). Only a few studies found significant differences in F0 and noise-related parameters such as NHR and HNR, depending on the nasal obstruction condition. Despite only being studied in one study, the parameters of SPI, VTI, DUV, DVB, vAm, and LTAS showed statistically significant results. This implies that these parameters, having not received sufficient interest, could be helpful for future research. In contrast, although extensively assessed, jitter demonstrated significant changes in only one study and exhibited limited sensitivity in this context. However, the lack of standard methods for voice recording, extracting parameters, and analyzing them continues to be a major methodological bottleneck that makes it hard to compare studies and create reliable, noninvasive assessment tools. For future studies, Machine learning (ML) models can be trained to recognize subtle acoustic patterns in the spectrograms that humans or traditional analysis methods may not easily detect. Spectrogram use in nasal obstruction assessment is a prominent method, as nasal obstruction alters the resonance characteristics of speech. Obstructed nasal passages may affect the nasal formants, particularly in nasal speech sounds and vowels. Thanks to spectrogram analysis, it is possible to capture the spectral consequences of nasal airflow impairment visually. For subjective voice evaluation parameters, VHI was the most widely used assessment. In three studies, it demonstrated a statistically significant improvement, with specific effects in subgroups. On the other hand, measures like GIRBAS and general patient-reported outcome yielded limited or descriptive findings. These results support the inclusion of both perceptual and patient-reported evaluations to comprehensively capture voice outcomes related to nasal obstruction. In conclusion, although preliminary evidence supports the use of acoustic voice analysis in the assessment of nasal obstruction, further research is needed to strengthen its validity, improve the accuracy of analysis tools, and develop standardized clinical protocols. The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app15158423/s1](https://www.mdpi.com/article/10.3390/app15158423/s1)]([https://www.mdpi.com/article/10.3390/app15158423/s1](https://www.mdpi.com/article/10.3390/app15158423/s1)), Figure S1: PRISMA flowchart; Supplementary File S1: List of excluded studies; Supplementary File S2: Quality assessment; Supplementary File S3: PRISMA checklist. Conceptualization, F.B., G.Y.-P., and P.L. ; methodology, G.Y.-P., C.C., and F.B. ; validation, G.Y.-P., E.D., C.C., and D.R. ; formal analysis, G.Y.-P. and F.B. ; investigation, G.Y.-P. and C.C. ; resources, G.Y.-P.; software, G.Y.-P.; data curation, G.Y.-P. and C.C. ; writing--original draft preparation, F.B., G.Y.-P., and P.L. ; writing--review and editing, F.B., G.Y.-P., C.C., P.L., L.B., E.D., and D.R. ; supervision, F.B. ; project administration, F.B.