The temporal organization of speech sounds, known as speech rhythm, has been a subject of interest among researchers. However, little attention has been paid to the variation of speech rhythm across different age groups. This study investigates the acoustic durational correlations of Persian speech rhythm in children (5–6 years old), adults (20–40 years old), and elderly adults (70–90 years old) using durational rhythmic metrics. Therefore seven durational rhythmic metrics were explored, including %V, nPVI-V, VarcoV, ΔV, nPVI-C, ΔC, and VarcoC. The findings reveal significant differences in all metrics across age groups. %V (proportion over which speech is vocalic) was the most distinctive metric, with children having the highest %V and adults the lowest. Children also displayed the greatest variation in the other measures of vocalic interval duration (ΔV, VarcoV, nPVI-V). The results indicate that vocalic interval metrics decreased from childhood to adulthood and then increased with aging, suggesting developmental and aging effects on vocalic interval control. On the other hand, the consonantal intervals (ΔC, VarcoC, nPVI-C) were not as consistent as vocalic intervals. Applying these metrics to Persian speech has elucidated the nuanced ways in which speech rhythm evolves from childhood through old age. The findings highlight the importance of considering age as a factor when studying speech rhythm and contribute to our understanding of the temporal organization of speech sounds across different age groups.