The Relationship Between Vertical Skeletal Patterns and Acoustic Distortion in Fricative Sound Production

Abstract

Objective: This pilot study aimed to investigate whether vertical skeletal patterns, as measured through cephalometric analysis, are associated with acoustic distortion in the production of the /s/ fricative sound among orthodontic patients. Methods: Thirty-three unselected orthodontic patients aged 13 to 26 were recruited from Jacksonville University School of Orthodontics. Each subject underwent cephalometric radiography to measure vertical skeletal variables, including PP-GoGn angle, Upper Anterior Facial Height (UAFH), Lower Anterior Facial Height (LAFH), and overbite (OB). Speech recordings were captured using an iPhone TrueDepth camera during the articulation of words containing /s/ and /sh/ fricatives. Acoustic data were analyzed in Praat software to extract spectral moment features: center of gravity (COG), standard deviation (SD), skewness, kurtosis, and the COG difference between /s/ and /sh/. Pearson-product moment correlations were used to evaluate linear associations between skeletal dimensions and acoustic measures. Results: A significant positive correlation was found between PP-GoGn and COG of /s/, suggesting steeper mandibular inclination is associated with higher acoustic frequencies. UAFH was negatively correlated with both COG and SD of /s/, indicating that reduced maxillary height may produce sharper, more distorted fricative acoustics. LAFH correlated negatively with skewness of /s/, and OB was significantly associated with kurtosis, reflecting energy dispersion changes. These structure-function correlations provide evidence of a measurable relationship between craniofacial form and speech acoustics. Conclusion: Vertical skeletal morphology significantly influences fricative sound production. Specifically, mandibular plane angle and anterior facial height appear to affect articulatory posture and oral cavity resonance, altering spectral properties of the /s/ sound. These findings highlight the importance of interdisciplinary collaboration between orthodontists and speech-language pathologists in evaluating and managing patients with malocclusion-related speech distortion.