The Phonetic Study of Rhythm in Persian

In this study, we investigated the acoustic correlates of rhythm in Persian. Two groups of sentences were designed that varied as to whether stressed syllables were separated by a number of unstressed syllables (Alternate Stress condition) or were in close proximity to one another (Stress Clash condition). The acoustic parameters related to F0 as well as mean intensity and mean duration were measured in the target syllables. Results suggested that both F0 and intensity have polar distribution in the Alternate Stress condition such that poles align with stressed and valleys align with unstressed syllables. In addition, all acoustic parameters displayed statistical differences between stressed and unstressed syllables across sequences of stressed-unstressed or unstressed-stressed syllables. On the other hand, results for the Stress Clash condition indicated that differences in F0 between stressed syllables in the sequences of adjacent stressed syllables are not significant, and that variation in F0 in such sequences does not result in polar distribution. Furthermore, while in the Stress Clash condition, the intensity of the second stressed syllable was significantly larger than that of the first syllable, the results were reversed for duration, meaning that the duration of the first syllable was significantly longer than that of the second syllable. Based on these results we suggested that sentences in the Alternate Stress condition are acoustically rhythmic as the distribution of acoustic measures results in alternate poles and valleys. However, no or little rhythm is found in the Stress Clash condition since F0 is neutralized and the other two parameters, namely intensity and duration function in the opposite direction.