Acoustic And Articulatory Study Of Ewe Vowels From A Multimodal Speech Database

In the present work,an articulatory and acoustic study of Ewe nasal and oral vowels were conducted in order to figure out how the oral and nasal distinction is manifested with regard to differences in lingual configuration and acoustic characteristics when produced by Ewe females on the one hand,and by Ewe males on the other.Besides,a comparative study of male and female,based on acoustic and articulatory data collected,was also conducted.First,a multimodal speech database of Ewe language was created by collecting data from 11 Ewe male speakers and 6 Ewe female speakers in laboratory settings,using Articulatory Assistant Advanced(AAA).Second,acoustic data were exported to Praat software for segmentation and labeling and then,using Linear Predictor Coefficients(LPC),the first two formant frequencies were extracted for analysis.The duration of each vowel was also measured.Regarding the articulatory data,tongue shapes were extracted from the ultrasound images and were analyzed using Smoothing Spline ANOVA(SSANOVA).Based on previous research,we expected to find evidence that all nasal vowels are produced with at least some change in lingual configuration compared to their oral congeners.The results have indeed shown differences in the vertical and horizontal position of the tongue;however,the difference is significant only for the vowel pair [a-?] and [?-??] for male participants,and only significant for the vowel pair [e-?],regarding the female participants.Results obtained from vowel duration analysis have revealed a significant difference between oral and nasal vowels for all the cases except for the vowel pair [e-?] produced by male participants.A comparison between gender revealed that the vowel duration is significantly higher for females compared to males.From the analysis of formant frequencies,we figured out that vowels are produced with a higher F1 and F2 frequencies by females when compared to males.We also observed from the acoustic results that F1 and F2 are higher for back-nasal vowels and lower for the front-nasal vowels,compared to their oral congeners,regarding the male participants.Concerning the female participants,F1 is lower for back-nasal vowels except for /?/ and higher for front-nasal vowels except for /?/ and /?/.The F2 frequency is lower for front-nasal vowels except /?/ while increased for back-nasal vowels except for /?/.This difference is significant for all the cases except for the vowel pair [?-??] produced by male speakers.However,the lack of acousticarticulatory mapping,observed during the production of some nasal vowels leads to the evidence of a combination of many articulators enhancing the effect of velopharyngeal coupling on F1 and F2 frequencies.