Objective: Glottal closure pattern is the most important stroboscopic sign for judgment about proper function of laryngeal function. Recent researches have suggested that complete glottal closure is not only normal glottal closure pattern. This research is aimed to investigate the closure pattern in normal subjects and the effect of phonation characteristics on it.

Materials & Methods: In this cross-sectional and description- analytical study, 80 people (58 females & 22 males) were selected by random from 218 students. After taking history, perceptual and voice self-assessment, those were selected that the assessments showed do not have any voice problems. Then videostroboscopic examination was performed and recorded during producing /i/ in habitual, high, low, loud and soft levels of phonation. Glottal closure patterns were analyzed and compared in different phonation in males and females by Fisher test.

Results: In general, complete closure was the most frequent pattern and Y posterior chink was the second one. The results revealed significant difference between male and female (P<0.001) and different phonation levels including habitual, high, low, loud and soft (P<0.001) in glottal closure pattern. Moreover, significant difference was observed in different levels of pitch in females (P<0.001) and in difference levels of loudness in males (P<0.001).

Conclusion: Incomplete glottal closure patterns, particularly Y posterior chink are not unusual findings in normal voice. Alternation in phonation levels can change glottal closure pattern significantly, therefore all of the phonation levels should be assessed in videostroboscopic examination, although it is not in the same manner in males and females