Fatemeh Azhdarzadeh - Musculoskeletal Rehabilitation Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Majid Soltani - Musculoskeletal Rehabilitation Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Negin Moradi - Musculoskeletal Rehabilitation Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
Davood Kashipazha - Department of Neurology, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

Acoustic analysis of speech is a powerful, noninvasive, and cost effective tool to study different aspects of motor speech disorders such as the dysarthria associated with Parkinson disease. This motor speech disorders resulted in mono loudness, mono pitch, hoarseness, harshness, breathiness, consonant imprecision and vowel centralization. f2i /f2u is an acoustic – articulatory scale that can be an appropriate instrument to distinguish dysarthric and normal speech. Materials and Methods: In this study, 40 individuals of Parkinson’s disease and 40 healthy individuals have been investigated. PD group was selected by an available sampling method by the diagnosis of neurologist and typeof dysarthria was diagnosed with Duffy’s protocol by two expertise people in motor speech disorders. Normal group was matched with age and sex with PD group. The task was repeating sentences including /i/ and /u/. Results: Individual with mean age 63±5.1 participatedin this voice evaluation. Statistics analysis showed difference in f2i/f2u between dysarthria and normal group (p value< 0.001). Conclusion: According to the nature of Parkinson disease and hypokinetic dysarthria vowel formant frequency going to be changed. One ofthe cost effective and noninvasive procedure to evaluate speech is computing f2i/f2u. this parameter can help early detection of dysarthtria and prevent its progress; and also help these people to improve their quality of life.