Between-speaker rhythmic variability is not dependent on language rhythm, as evidence from Persian reveals

Abstract

Acoustic measures of speech rhythm based on the durational characteristics of consonantal and vocalic intervals (henceforth C- or V-intervals) as well as syllabic intensity reveal between-speaker variability. The evidence obtained so far is based on speakers of stressed-timed languages, which are assumed to have complex consonant clusters and a higher degree of vowel reduction. Speakers of stressed-timed languages might operate their articulatory organs in different ways due to the syllable complexity and vowel reduction. Complex consonant clusters are released differently, and vowel reduction tends to be produced more or less strongly depending on speakers. When a language lacks such features, it is possible that rhythmic variation between its speakers decreases. In the present study, we aimed at exploring between- and within-speaker rhythmic variability in Persian, an Indo-European language categorised as syllable-timed. Acoustic correlates of speech rhythm (%V, ΔV[ln], ΔC[ln], n-PVI-V) and articulation rate were obtained from two Persian corpora with different sources of within-speaker variability. In the first corpus, the source of within-speaker variability mainly comes from non-contemporaneous recording sessions, and in the second corpus, from different speech rates. Results revealed that there were significant differences between speakers in all investigated speech rhythm measures in Persian and %V best discriminated between speakers. This reveals that the lack of typical stress-time features does not affect between-speaker variability in speech rhythm.