maintain distinct characteristics or merge with the characteristics of the existing stop consonants in Assam Sora.
glottal stop /P/. The pre-glottalized consonants are only allophonic variation of the non-glottalized consonants which occur in the word final position only. Thus, it is more likely that a glottal stop /P/ is the actual glottal phoneme in Munda languages, whereas the pre-glottalized consonants are only allophonic variation of the non-glottalized stop consonants in Munda languages.
Additionally, other important characteristics of the glottal constriction in Munda languages is reported in a South Munda language namely Gorum. Rau (2011) argues, glottal constriction in Gorum is realized as three distinct glottal phonemes including a glottal stop /P/, a pre-glottalized voiced obstruent /PO/ and creaky vowels /V
˜/.
Evidences suggest, while the glottal stop and the creaky vowels are clear glottal phenomena differing only in the degree of glottal constriction, the pre-glottalized onstruents which occur in the boundary between a vowel and a non-glottalized voiced stop appear as complex sounds. Also, Rau (2011) proposes that the three glottal sounds are essentially consonant phonemes in Gorum, and are related to the syllable structure and prosodic structure of the language. Evidences suggest that only one glottal element is allowed in a syllable, and it is confined to the syllable rhyme of the word. Likewise, syllable weight is also attributed to the syllable which consists of the glottal element. Thus, it is evident that glottal constriction is a significant phenomena in Gorum, and evidences suggest that unlike other Munda languages Gorum exhibits an extensive phonologization of the three glottal elements.
In case of Assam Sora, the overview of the consonant phonemes, in Section 2.2.5 of Chapter 2 reveals that, similar to Orissa Sora, Assam Sora also has only one glottal element, namely the glottal stop /P/. Also, evidences suggest that the glottal stop in Assam Sora mainly occurs word medially and word finally. Additionally, as part of this research work, acoustic phonetic characteristics of the glottal in Assam Sora are also presented in Kalita et al. (2016). This study primarily classifies the glottal stop in Assam Sora on the basis of its phonetic properties. The study propose acoustic
features which helps in identifying the glottal stop in Assam Sora speech data. Thus, some of the major findings reported in the study are described in the following section.
5.4.1 Phonetic realization of /P/ in Assam Sora
The study by Kalita et al. (2016) mainly examines intervocalic glottal stops in Assam Sora. This includes disyllabic words such as uPu meaning hair, iPi meaning louse, daPa meaning water etc. The study reveals that intervocalicaly, the glottal stop in Assam Sora has three different phonetic realizations including a complete voiceless glottal stop, a voiced glottal stop and a creaky voiced glottal stop. A wave form captured while producing the word iPi, in Assam Sora, illustrates the presence of a complete voiceless glottal stop in Assam Sora in Figure 5.7.
Figure 5.7: Wave form showing complete glottal stop in the word iPi
Figure 5.7 shows that periodic wave forms, representing vowel sounds, are com- pletely ceased during the production of the glottal stop in the wordiPi. This indicates that the glottal stop is able to interrupt the voice source by completely closing the vocal folds for a certain period of time. Following this when the glottal constriction is released, the vocal folds start vibrating again resulting in resuming of the periodic waves. Thus, as indicated in Figure 5.7, a complete voiceless glottal stop in Assam Sora is characterized by the absence of acoustic energy, caused by an occlusion at the source of the sound namely, the glottis. Therefore, a complete voiceless glottal stop in intervocalic position can be clearly discriminated from the adjacent vowel sounds in Assam Sora.
The second type of glottal stop in Assam Sora is a voiced glottal stop. The voiced glottal stop is distinct from the complete voiceless glottal stop because unlike the complete voiceless glottal stop, the voiced glottal stop does not completely interrupt the voice source. Rather, in voiced glottal stops continuous voicing over the glottal stop region is observed. This realization of the glottal stop in Assam Sora can be seen in Figure 5.8, which shows the wave form of the voiced glottal stop captured during production of the word iPi in Assam Sora.
Figure 5.8: Wave form showing voiced glottal stop in the word iPi
Figure 5.8 shows that glottal occlusion during the production of voiced glottal stop is not as prominent as it is in case of the complete voiceless glottal stop. This indicates, in voiced glottal stops the vocal cords are not completely occluded, and therefore they continue to vibrate. As a result, glottalic cycles of the preceding vowel are carried over the glottal stop and continued onto the following vowel sound. However, due to a pressure of creating a glottalic occlusion, amplitude of the speech signal where the glottal stop occurs is relatively lower than the adjacent vowel segments. Thus, besides having the voiced characteristics of the adjacent vowels, voiced glottal stop in intervocalic position is also characterized with a low amplitude in Assam Sora.
The third type of glottal stop in Assam Sora is a creaky voiced glottal stop. The creaky voiced glottal stop is similar to the voiced glottal stop in Assam Sora. The creaky voiced glottal stop also has continuous voicing, but unlike the voiced glottal stop, it is characterized with abrupt changes in the voice source. The abrupt change in the voice source during the production of creaky voiced glottal stops distinguishes it from the voiced glottal stop. A wave form of the creaky voiced glottal stop captured
while producing the word iPi, in Assam Sora, is presented in Figure 5.9.
Figure 5.9: Wave form showing creaky voiced glottal stop in the word iPi
Figure 5.9 shows that some interruption is caused during the production of a creaky voiced glottal stop, but the interruption is not as significant as it is seen in case of the complete glottal stop. Creaky voiced glottal stop allows continuation of vocal cords vibration from the preceding vowel to following vowel. However, the pressure to make the glottal occlusion is so strong that the acoustic energy is significantly lowered at the point where the creaky voiced glottal stop occurs intervocalicaly. Consequently, the voice source abruptly changes at the point where the creaky voiced glottal stop occurs. Additionally, creaky voiced glottal stop in Assam Sora also exhibits a variation in its pitch pattern. Figure 5.10 shows the pitch extracts of the creaky voiced glottal stop captured while producing the word iPi in Assam Sora.
The top panel in Figure 5.10 shows that the creaky voiced glottal stop has a rising pitch. And the bottom panel shows that the creaky voiced glottal stop has a dipped pitch. This indicates that abrupt changes in voice source during the pro- duction of creaky voiced glottal stop also perturbates pitch variation. In this regard, (Hillenbrand & Houde, 1996) proposes that pitch perturbation is natural phenomena in intervocalic glottal stops. Also, evidences suggest that a dip pitch is perceptu- ally more prominent then a rising rising pitch in identifying intervocalic glottal stops in continuous speech. Thus, perturbation of pitch pattern during the production of creaky voiced glottal stop is an important phonetic characteristic which helps in identifying intervocalic glottal stops in Assam Sora.
Figure 5.10: Two types of pitch patterns in creaky voiced glottal stop