4.5 Assam Sora vowel formants in individual syl- lables of disyllableslables of disyllables
4.5.1 F1 and F2 of similar vowels in individual syllables of disyllablesdisyllables
In order to examine how syllable position effects Assam Sora vowel formants, F1 and F2 frequencies of the six vowels in first and second syllable are plotted next to each other on the same vowel plot. This helps in visualizing the effect of syllable position on Assam Sora vowel formants. Thus, region-wise Assam sora vowel plots across first and second syllable are presented in Figure 4.2.
From Figure 4.2 it is evident that Assam Sora vowels are positioned differently in first and second syllable of disyllabic words. When Assam Sora vowels in first and second syllable are plotted next to each other, it is observed that all the vowels are either raised or fronted in one of the two syllables. For instance, the mid central vowel /@/ is always produced higher in first syllable than in second syllable. Similarly, the mid front vowel /e/ and the low central vowel /a/ are usually positioned higher in first syllable than in second syllable, except in the vowel plot representing Sessa speakers.
Likewise, the mid back vowel /o/ is usually positioned fronter in first syllable than in second syllable in all the vowel plots, except in the vowel plot representing Sessa speakers. Therefore, it is observed that similar vowels in first and second syllable are
Figure 4.2: Assam Sora vowels in 1st and 2nd syllable
Vowels: i=/i/, e=/e/, a=/a/, o=/o/, u=/u/, Ee=/@/
distant from each other to a certain extent. Thus, by examining Assam Sora vowels separately in first and second syllable of disyllabic words it is revealed that Assam Sora vowels exhibit dynamic nature across first and second syllable of disyllabic words. It is found that, similar vowels in first and second syllable are distant from each other in terms of their F1 and F2 frequencies. Also, this dynamic nature of Assam Sora vowel system is observed regularly in Assam Sora vowel data recorded in all four regions.
However, an exception is found in the Sessa data where the patterns are not similar to the patterns observed in rest of the regions. In this regard, the present work could not find an explainable result, but it is noticeable that despite the exceptions, the primary argument is not effected.
Thus, in order to similar vowels have some degree of perceptual distance, euclidean distance between similar vowels in first and second syllable is calculated for Assam Sora vowel system. Euclidean distance is a mathematical measurement used for calcu- lating distance between any two points in a given space. In case of vowel descriptions, euclidean distance measurement is commonly used to show the perceptual distance between two vowels in the F1 and F2 plane of a vowel space (Lindblom, 1986). In other words, euclidean distance basically measures the distance between the points which represent the position of two vowels in a vowel plot. Also, since vowel points represent a combination of F1 and F2 frequencies, the distance considers both F1 and F2 frequencies of the two vowels for which the euclidean distance is calculated.
Therefore, euclidean distance between two vowels represent the combined effect of F1 and F2 frequencies of the two vowels. Thus, in order to estimate the perceptual dis- tance, euclidean distance between similar vowels in first and second syllable of Assam Sora disyllables is calculated using equation 4.2.
eud= q
(F1x−F1y)2+ (F2x−F2y)2 (4.2) In equation 4.2 eud represents the euclidean distance between two vowels based on their F1 and F2 frequencies. F1x, F1y and F2x, F2y represent the F1 and F2 frequencies of the two vowels between which the euclidean distance is calculated. Ta- ble 4.7 presents the region-wise euclidean distance estimation between similar vowels across first and second syllable in Assam Sora disyllables.
The euclidean distance estimation in Table 4.7 provides evidence that Assam Sora vowel formants differ across first and second syllable of disyllabic words. Table 4.7
Table 4.7: Euclidean distance between similar vowels across syllables Singrijhan Sessa Koilamari Lamabari
i-i 18.07 13.91 15.14 4.95
e-e 56.63 42.54 80.95 65
a-a 42.48 15.36 50.32 48.53
o-o 43.33 35.18 46.84 53.87
u-u 33.09 46.62 28.54 32.03
@-@ 28.74 21.75 42.64 20.25
reveals that, considerable perceptual distances between similar vowels across first and second syllable of disyllables exists in all six vowels of Assam Sora. As a result, Assam Sora vowel properties such as vowel height, vowel frontness/backness are often changed as a function of syllable position as it is seen in Figure 4.2. This indicates that syllable position has a significant role in vowel characteristics of Assam Sora. Also, it is observed that perceptual distances between similar vowels across first and second syllable of disyllables exists in Assam Sora speech variety of all four regions including Singrijhan, Sessa, Koilamari and Lamabari. This confirms that that changing of vowel formants to certain degree across first and second syllable of disyllabic words is a general tendency in Assam Sora vowel system and the analysis here provides adequate evidences for this phenomenon.
Additionally, it is observed that variation in either F1 or F2 frequency also causes some of the vowels to move away from their canonical positions and to come closer to their adjacent vowels. This can be seen in Figure 4.2 where mid front vowel /e/
is often closer to the high front vowel /i/ in first syllable but not in the second syllable. This indicates that, in addition to changing the vowel quality of individual vowels, syllable position also effects the perceptual distance between adjacent vowels within individual syllables. Thus, in order to examine how syllable position effects the perceptual distance between adjacent vowels within individual syllables, vowel formants of adjacent vowels in first and second syllable are examined in the following section.