Impact of prominence type on the coarticulation of vowels following palatalized consonants

The quantitative impact of prominence (neutral vs emphatic stress) on the coarticulation of the Russian low æ, mid e and high i front vowels is evaluated in CV sequences with palatalized consonants of various places of obstruction. The research is conditioned by the aims of speech synthesis and recognition of the Russian language, the current data in the field being insufficient. First order linear equations (locus equations) are used to evaluate the degree of CV coarticulation. The experiment is performed on CjVCjV nonsense words imbedded in the middle position of a carrier phrase «Vyros CVCV sjyljnym» («CjVCjV has grown up strong»). The first syllable of the target words was uttered both with neutral and emphatic stress. The Praat software was used to measure F2 formant values at vowel onsets and central parts. It was established that linear regression slopes are similar both in the Y-intercepts and slope coefficients for the palatalized consonants of various places of obstruction uttered with the same prominence. The degree of coarticulation was different depending upon the type of prominence (neutral or emphatic): the coefficients were lower in case of the emphatic stress compared to those of the neutral one. ANOVA analysis and Student’s t-test were performed to reveal the difference in F2 values of vowel onsets and middle parts as a function of the vowel openness and type of prominence. The results obtained were interpreted based on the degree of the openness of the vowels under study: an open vowel under emphatic stress tends to expand its vowel space by a backward displacement while close vowels tend to move forward in the mouth cavity when pronounced with emphatic stress.