Coordination between the larynx and lower airways is essential for normal voice production. Disorders in vocal pathways or air pathways may ruin this coordina-tion. Vocal cord dysfunction (VCD) serves as an example, which is characterized by full or partial vocal fold closure that usually occurs for short periods during inhalation but can also occur during exhalation. And one of its physiological etiolog-ies is laryngeal hyper responsiveness, brought on by a range of different triggers that cause inflammation and/or irritation of the larynx (Barbara A. Mathers-Schmidt Paradoxical Vocal Fold Motion,May 2001). Also changing in normal voice affects’ pulmonary functions ( Soren Y. L.
2005) studied the difference in respiratory and laryngeal function during spontaneous speaking for teachers with voice disorders compared with teachers without voice problems. In this study respiratory function was measured with magnetometry, and laryngeal function was measured with electroglottography during 3 spontaneous speaking tasks. And she concluded that teachers with voice disorders started and ended their breath groups at significantly smaller lung volumes than teachers without voice problems during teaching-related speaking tasks. Some studies compared voice parameters with pulmonary parameters in patients that underwent a partial laryngectomy surgery and healthy persons. (Mehmet.G .D .
et al ,2016) . They compared FEV1 (Forced expiratory volume in 1 second), FVC(Forced vital capacity), FEV 1 / FVC and FEF (Forced expiratory flow) with jitter and shimmer values and maximum phonation time (MPT). The pulmonary function test was affected in 75 % of patients underwent supracricoid laryngectomy.
They conducted that, laryngectomy operation leads to a decrease in maximum phonation time due to incomplete glottal closure 4,6-8,10,23. In their study, MPT value was 29,83 sec, while it was observed to decrease to 15,7 in patients underwent to partial laryngectomy.They thought that the reason for this reduction is associated with both decrease in lung capacity and defects in glottal closure. Creating a correlation between forced vital capacity and maximum phonation time compared to waist circumference and nutritional status was the purpose of (Frenanda. D.
S and her colleagues, 2016). In their cross-sectional study of 82 children aged between eight and ten years. Evaluated and correlated forced vital capacity and maximumphonation time in relation to abdominal circumference and nutritional status of children. They conducted that the forced vital capacity was higher in children with higher abdominal circumference (p = 0.003) and percentiles of abdominal circumference 25-75 had longer sustain the vowels (p <0.
05). No statistically significant difference in forced vital capacity and TMF /e,a,?/ in relation to nutritional status.There was strong correlation between /a/ maximum phonation time and maximum phonation time /e/ (0.84). Previous studies as shown concerned with finding relationships between voice parameters(MPT, s/z ratio, jitter and shimmer) and pulmonary parameters(FVC , FVC1, FEE ) , (Mehmet.G .D .
2016), and (Frenanda. D. S , 2016 ) in patients with abnormalities and in children in relation to abdominal circumference . Our study aiming for finding if there is correlation between voice function parameters (fundamental frequency, jitter and shimmer) and lung function parameters (FVC ,FVC1, FVC ratio ) in normal persons who don’t suffer any vocal or respiration circumstances .