Background and aim: Muscles that contribute in production of sound have an important role in specific language. Knowledge of normal activities of these muscles is very important in language dysfunction and pathologic conditions. Needle electromyography is complementary approach in clinical evaluations of above conditions but it is a painful method for evaluating of the patient. Surface electromyography can be used to neurophysiological behaviors and effect of treatment interventions and is accepted by scientific academies. The purpose of this study is appointment of new approach in this area.

 Materials and methods: Sixty eight healthy subjects (34 female and 34 male) in range of 20-30 years old were contributed after supplement of questioner form in this study. Subjects sat in a chair with arm rest and recording electrodes placed on muscles of Thyroarytenoid and Cricothyroid of both side (right and left) at middle and lower parts of throat, near of 1 cm from midline.  Silent activity and fricative voice (z-zh) and voiceless (s-sh) activities recorded randomly at 10 second with interval rest between them for 5 repetition. All of signals processed and then compared in time, frequency and non linear measurements.

 Results: Non linear values such as Percent of recurrence, Entropy were reduced significantly in fricative voice (P<0.05).

 Conclusion:  Surface activity recording of Thyroarytenoid and Cricothyroid muscles is possible and sensitive parameter is non linear values. Surface electromyography is new approach for assessment of above muscle in clinical evaluation of speech pathologic conditions.