4.5 Assam Sora vowel formants in individual syl- lables of disyllableslables of disyllables
4.5.3 Assam Sora vowel space in individual syllables of di- syllables
Hence, by examining the euclidean distance between some of the adjacent vowels in Assam Sora vowels system it is revealed that perceptual distance between adjacent vowels is often minimized or maximized as a function of syllable position. It evident that front vowels are relatively close to each other in first syllable, but separated further in second syllable. Similarly, the central vowels are relatively closer to each other in the first syllable than in the second syllable. Likewise, the back vowels also have different distances from the mid central vowel depending on their syllable position in disyllabic words. Moreover, in addition to these vowels, it is confirmed that perceptual distance between all adjacent vowels in Assam Sora vowels system is reduced or expanded to a certain degree as a function of syllable position. Hence, as per the predictions of Adaptive Dispersion theory that vowel system may restructure depending on the maximization and minimization of perceptual contrast between vowels, it is likely that the overall shape and structure of Assam Sora vowel system will also differ across syllables. Therefore, in order to examine the overall impact of syllable position on Assam Sora vowel system, Assam Sora vowel area space in disyllables is analyzed in the following section.
4.5.3 Assam Sora vowel space in individual syllables of di-
within which all the vowels of a vowel system are contrastively perceived in a lan- guage. Therefore, in the description of vowel systems, vowel space is often analyzed in order to to examine the difference in vowel system of two dialects (Jacewicz et al., 2007) or to examine gender variations in the vowel system of a particular language (Lengeris, 2016). Thus, analysis of vowel space provides information about the over- all shape and structure of vowel systems. Also, comparison between vowel spaces of two vowel systems provide evidence regarding similarity or dissimilarity in the overall shape and structure of the vowels systems. Hence, considering the fact that Assam Sora vowel formants change across syllables, it is relevant to examine whether the overall shape and structure of the vowel system also changes as a function of sylla- ble position. Therefore, this section examines the vowel space of Assam Sora vowel system in first and second syllable of disyllabic words.
In order to visualize the overall vowel space of Assam Sora vowel system in first and second syllable all the vowel points in each of the two syllables are plotted next to each other with closed circumferences. The vowel plots include all vowel tokens in first and second syllable and all vowel formants are also normalized for speaker effect using vowel normalization method proposed by Lobonov (1971). Thus, the region- wise vowel plots presented in Figure 4.3 represent the overall vowel space plots for Assam Sora vowel system in first and second syllable of disyllabic words.
From Figure 4.3 it is evident that the overall vowel spaces of Assam Sora vowel system in first and second syllable are fairly similar. However, in order to compare the actual vowel space in first and second syllable, vowel area space of Assam Sora vowel system in the two syllables is estimated. For this purpose, the vowel syatem is divided into three parts representing three vowel triangles such as /i-e-a/, /i-a-u/
and /u-o-a/. Then area of the three vowel triangles is calculated using equation 4.3.
area=p
s(s−a)(s−b)(s−c) (4.3)
Figure 4.3: Assam Sora vowel space in first and second syllable
Vowels: i=/i/, e=/e/, a=/a/, o=/o/, u=/u/, Ee=/@/
In equation 4.3 ‘a’, ‘b’,‘c’ represent lengths of the three sides of a vowel triangle and ‘s’ represents the summation of a, b and c or (a+b+c). Also, lengths of the three sides of every vowel triangle basically represents the euclidean distance between two vowel points. For example, in the the vowel triangle /i-e-a/, ‘a’ represents the
euclidean distance between /i/ and /e/,‘b’ represents the euclidean distance between /e/ and /a/ and ‘c’ represents the euclidean distance between /a/ and /i/ in the vowel triangle. Subsequently, after calculating the area of the three vowel triangles in a vowel system, overall vowel area space of the vowel system is estimated by adding the areas of the three vowel triangles. Estimated vowel area space of Assam Sora vowel system in first and second syllable of disyllabic words is presented in Table 4.11.
Table 4.11: Vowel area estimation in first and second syllable Singrijhan Sessa Koilamari Lamabari σ-1 33765.48 30979.57 32858.72 26708.66 σ-2 39110.32 22235.24 41111.6 35219.97
Estimation of vowel area space presented in Table 4.11 reveals that vowel area space of Assam Sora vowel system is essentially different in the first and second syllable of disyllabic words. This indicates that, the vowel space encompassing all the vowel sounds in Assam Sora vowel system is normally effected as a function of syllable position. Consequently, it is observed that vowel area space is usually larger in second syllable than in first syllable except in case of Assam Sora vowel data recorded from Sessa where a reverse relation is observed. In this regard, it has been observed that Assam Sora speakers living in Sessa frequently use an Indo-Aryan language namely Sadri and it is likely that their bilingual ability is influencing their native language.
However, more evidences are required to investigate this speech behaviour, and since the vowel properties discussed so far have not shown any significant difference, it is argued that there are no regional variations of Assam Sora based on its vowel properties. On the other hand, a usually larger vowel space in second syllable can be convincingly related to the the phonetic prominence of second syllable over first syllable. As it is shown in Section 3.4 of Chapter 3, the second syllable is phonetically more prominent than first syllable in Assam Sora disyllables. It is proposed that the phonetic prominence of second syllable is influencing the vowel area space of Assam
Sora vowel system. Thus, except in vowel data of Sesss speakers, vowel space of Assam Sora vowel system is always larger in the second syllable and smaller in the first syllable. However, despite the exception in Sessa data, the general analysis of Assam Sora vowel formants in this work adequately confirms that syllable position in disyllabic words is an essential factor effecting the vowel system of Assam Sora. Hence, it is clearly evident that syllable position not only effects the formant frequencies of individual vowels in the two syllables, but it also effects the overall shape and structure of Assam Sora vowel system.