The main aim of this article is to introduce a phonetic and phonological methodology to recognize vowels from speech data of an informant belonging to a dialect region. To this end, Abuzeydabadi dialect is chosen because of its richness in vowel variations. Given the prediction of the auditory dispersion theory, a native speaker of Abuzeydabadi was asked to produce appropriate minimal pairs in interaction with the researcher. Audio and video of the speech data were recorded. Distinctive vowels and their corresponding symbols, according to cardinal vowels trapezoid, were identified cautiously by investigating first, second and third formants, acoustic rules governing them and observing lips shape. The process extended from universal vowel triangle to vowel polygons until 15 Abuzeydabadi vowels were recognized, 12 of which were short and 3 were long. In general, lip shape, tongue root position, centrality and length have led to the extension of the vowels in Abzeydabadi. Minimal n-tuplets and formant frequencies illustrate that lip shape is distinctive for close front and mid front vowels. In addition, advanced and retracted root of tongue contrast for close front vowel. Low central vowel [ɐ] and round mid central vowel [ɵ] are among most frequent central vowels in our research data. Evidence was also obtained for the phonological function of length for the central vowels [ɵː] and [ɐː] and the vowel [eː].