Acoustic Analysis of Long Vowels in Jordanian Arabic With Class III Malocclusion.

Purpose: This study examined the acoustic properties of long vowels /ā/, /ū/, and /ī/ adjacent to labiodental and interdental fricatives (/f/, /θ/, /ð/, and /ðˤ/) in Jordanian Arabic speakers with Class III malocclusion compared with those with normal occlusion.

Method: Fourteen untreated or early-stage treatment participants with Class III malocclusion and 14 with normal occlusion, representing both sexes, produced 24 consonant-vowel-vowel-consonant monosyllabic words containing the target vowels. Acoustic parameters, including vowel duration and the first three formant frequencies, were analyzed using Praat software.

Results: In the environment of /ā/, Class III malocclusion speakers exhibited lower third formant frequency (F3)-mid values than those with normal occlusion. The formant frequencies of /ū/ were significantly affected, with higher F1 and F2 and lower F3 in Class III malocclusion cases. For /ī/, speakers with Class III malocclusion showed higher F1-mid, F2-onset, and F2-midpoint values.

Conclusion: The findings suggest that Class III malocclusion alters vowel acoustics, particularly in formant frequencies, contributing to a deeper understanding of its impact on speech production and informing speech therapy interventions.