Between-speaker variability of voiceless fricatives in Persian

Fricatives not only differ in their acoustic structures from one language to another, but also they vary considerably from individual to individual. Acoustic correlates of fricatives are sensitive to the shape and size of the resonance cavity in front of the oral constriction. It is therefore conceivable that any physical change in the length and place of constriction during production of fricatives may alter the resultant acoustic signals. This research attempts to explore potential speaker-specific acoustic parameters of voiceless fricatives in Persian based on experimental phonetics. Therefore, acoustic parameters of center of gravity and fricative duration are investigated for each voiceless fricative in Persian. This research aims to discover whether voiceless fricatives and selected acoustic parameters are able to discriminate between speakers in Persian and whether these fricatives and acoustic parameters are of assistance in segregating speakers in Persian. According to the aforementioned considerations, the following questions are presented in this paper: Do the selected acoustic parameters (center of gravity and duration) of voiceless fricatives have capacity to differentiate speakers in Persian? Which acoustic parameters and which voiceless fricatives discriminate Persian speakers the best? Furthermore, we will compare the results of the present study to the findings of previous studies to see in what way Persian has been similar or different from other investigated languages. In order to analyze between- and within speaker variability of voiceless fricatives, 24 Persian speakers (12 male, 12 female) on two separate occasions were recorded in the sound proof booth at phonetics laboratory of Alzahra University. Non-contemporaneous recording of speech material allows us to measure the degree of within-speaker variability across each speaker. The speech material consists of a read passage which contains 54 Persian sentences including relevant voiceless fricatives Speech tokens were acoustically measured with PRAAT version 5.2.34 and statistical analyses were carried out with SPSS version 21 and R version 3.3.3.Results and Results of this study indicated that for female speakers, center of gravity of /S/ and s/  have the best performance in showing between-speaker variability. For male speakers, center of gravity of /s/ is the most highly discriminant acoustic parameters across speakers. Moreover, fricative duration was not reported as a promising acoustic parameter. Center of gravity is directly linked to the size and length of the vocal tract. The longer is the length of the vocal tract, the higher is the center of gravity and vice versa. This indicates that anatomical differences between speaker’s vocal tract influence the acoustic properties of fricatives and ultimately make them distinctive. In the future studies, additional parametric potential speaker-specific features will be examined in order to determine a set of well-established discriminant parameters for voiceless fricatives in Persian.