ABSTRACT
Formant structure is one of the most important acoustic characteristics of Sounds. We can differentiate Vowels according to their first three Formants. Objective measurements of Vowel Formants are more valid than auditory perception in pathologic circumstances including children with hearing impairment. In this analytical-descriptive and cross-sectional study we compared the Persian Vowel Formants between 64 Normal and hearing impaired students ranged from 15-18 years Old in Esfahan high school. The mean of Fl, F2, F2/F1 and F3/F1 of Persian vowels in all groups were significantly different [P<0/05]. The mean of F3 of Persian vowels only in/u/ was significantly different. Results showed that students with moderate and severe hearing impairment had an irregular pattern of vowel arrangement in regard of the most and the least three formants [Fl- F2 - F3]. They also tend to substitute forward vowels with backwards and near the vowels place of articulation to back of the tongue and making sclnowa because of their dependence on proprioceptive sense while making sound