As part of an investigation of the coarticulatory influence of "lingual" consonants on the quality of adjacent vowels in MSA, measurements were made of Fl & F2 of all the vowels in CV-structure real words pronounced by native Arabic speakers from different countries. It was found that Fl in vowels preceded by interdentals, dentals, palatals and post-palatals was lower than that in vowels preceded by emphatics, velars, uvulars and pharyngeals. F2, however was found to be higher in vowels following interdentals, dentals, palatals and postpalatals than in those following emphatics, uvulars and pharyngeals. Based on these findings, a binary classification of MSA vowels is proposed in terms of the correlation between tongue movements and acoustic-phonetic variance.
Bibliographic reference. Znagui, Imad / Boudelaa, Sami (1993): "Towards an acoustic-phonetic classification of modern standard arabic vowels", In EUROSPEECH'93, 425-427.