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Introduction Speech is a system of verbal communication and is distinct to human beings. Speech sounds comprise of vowels and consonants. Among consonants, stops are produced by the complete occlusion of the oral cavity by articulators. Acoustic characteristics of stops include closure duration, voice onset time (VOT), release burst and formant transition VOT is a strong cue to voicing differences between stops (Lisker & Abramson 1964, 1970). OT values differ according to the place of articulation and voicing. VOT is longer in a high vowel context than in a low vowel context (Smith, 1978). Dysarthria is a speech disorder caused by muscle weakness due to brain damage. Voice onset time (VOT) is measured as the time interval between the release burst and the first quasi periodicity in the acoustic signal (Lisker & Abramson, 1964; Keating, 1984; Klatt, 1975). VOT is a objective acoustic measure used to measure motor speech control. It has been used to measure the timing between the structures of larynx and oral cavity in normal and as well in individuals with speech disorders. The measurement of voicing contrast between Dysarthric patients and normally speaking young adults facilitates the differentiation of the voice quality between variants of dysarthria. VOT measure indicated in the assistance of planning a proper rehabilitation program for dysarthric patients with voice disorder by ruling out their pattern of VOT and to determine whether the administration of dopaminergic medication aﬀected VOT separation in speakers with P.D. Aim & Objectives. The present study aimed at measuring the difference voice onset time across normal adults and individuals with spastic and flaccid dysarthria (IWD). Method Participants A total of 66 participants were considered in the study divided into three groups. Group I consisted of 30 adult males in the age range of 18-40 years. Group II consisted of 30 adult females in the age range of 18-40 years and group III consisted of 6 individuals with dysarthria. All the normal male and female participants had no history of any structural and functional abnormalities of the oral mechanism and had no speech, language or any neurological impairment. A set of 6 VCV syllables with plosives /p/,/t̪/,/k/ and their voiced cognates /b/,/d̪/,/g/ in vowel contexts /a/ (/apa/, /ata/, /aka/, /aba/, /ada/, /aga/) were considered as the material. Thus, each participant was made to produce these 6 VCV syllables for five times each. The recordings were carried out in a quiet room using a high-quality Microphone (iBall i342MV). The microphone was kept at a constant distance of 10 cm from the mouth of the speaker. The participants were familiarized with the test stimuli and were instructed to utter the stimuli VCV tokens for five times at a comfortable loudness level and pitch. Demonstration were provided by the clinician. A certain number of trials were given to the participants in case of unsatisfactory production. These recording condition were consistent during whole collection process. VOT measurements were made using PRAAT software program.VOT measurements were made directly from the spectrograms by measuring the distance between the release of the plosive to the onset of voicing of the following vowel in each syllable. Upon the statistical analysis, the mean values of VOT for the voiceless plosives were as follows. The phoneme /p/ were 24.13msecs, 19.85msecs and 69.89msecs in normal female, male and IWD respectively. The mean values of VOT for the phoneme /t/ were 24.68 msec, 17.16msec, 62.78msec respectively for males, females and IWD respectively. The mean values of VOT for phoneme /k/, were 27.90msec, 20.00msec and 61.97msec in normal female, male and IWD respectively. The voiced phonemes /b, d, g/ had mean values which were lesser than the voiced cognates. Mean values of VOT of /b/ were 17.48msec, 13.36msec, 31.97msec among normal male, female and IWD respectively. For phoneme /d/, it was 18.40msec, 12.35msec and 8.97msec respectively for normal male, female and IWD. The phoneme /g/ had 19.20msec, 14.99msec and 16.45msec among normal male, female and IWD respectively. Conclusion The present study profiled the VOT measures in flaccid and spastic dysarthria. The variable trends noted in the VOT values suggested the reduced neuromuscular integration of laryngeal and articulatory coordination.
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