en گفتار درمانی Speech therapy پژوهشي Original Research Articles <strong>Objectives</strong>: In the early stages, most Parkinson&rsquo;s patients display some degrees of voice and speech disorders. Speech disorders can negatively affect individuals&rsquo; social interactions and life; thus, treatment plans for the disorders in the early stages might be further beneficial than the late stages. Therefore, we aimed to investigate the effects of an intervention on Persian-speaking patients with early mild Parkinson&rsquo;s Disease (PD). The intervention was the Lee Silverman Voice Treatment (LSVT).<br> <strong>Methods</strong>: This was an interventional study and included 23 patients with PD. The study participants were randomly assigned into one of two groups; 13 patients in the intervention group (PD-I), and 10 in No-Intervention (PD-NI) group. Normal Persons (NP) or the control group included 13 healthy participants who were neurologically normal and presented no speech and voice disorders. Besides, they were matched with the PD-I group concerning education, age, gender.<br> <strong>Results</strong>: There was a significant impairment in Maximum Phonation Time (MPT), vocal loudness in vowel /a/, in reading, and during a monologue speech in the PD group, compared with the NP group (P&le;0.001). The LSVT resulted in a significant improvement in all measures in the PD-I group (P&le;0.001); however, no significant change was observed between the PD-I and PD-NI groups&rsquo; scores in first assessment (P&ge;0.201). In contrast, the PD-NI group&rsquo;s results in all measurements of final assessment were significantly lower than those in the PD-I (P&le;0.001) and NP (P&le;0.001) groups. The MPT also exhibited a considerable improvement in the PD-I group, compared with the controls.<br> <strong>Discussion</strong>: The LSVT, as a therapeutic technique based on the motor learning theory was beneficial in improving the vocal loudness of Persian-speaking patients with PD in the early stages of their disease.<span dir="RTL"></span><span dir="RTL"></span> Voice, Treatment, Loudness, Voice disorders, Parkinson disease 75 84 http://irj.uswr.ac.ir/browse.php?a_code=A-10-1107-1&slc_lang=en&sid=1 Younes Amiri Shavaki amiriyoon@yahoo.com 0000-0003-0380-2474 No Department of Speech and Language Pathology, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran. Arezoo Saffarian asaffarian_slp@yahoo.com 0000-0003-1749-2446 Yes Department of Speech and Language Pathology, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran. Gholam Ali Shahidi shahidi.g@iums.ac.ir 0000-0002-3889-4973 No Movement Disorders Clinic, Hazrat Rasool Hospital, Iran University of Medical Sciences, Tehran, Iran. Mohammad Reza Keyhani More_Keyhani@yahoo.com 0000-0003-3696-295X No Department of Basic Sciences, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran.