Electroglottographic contact quotient in different phonation types using different amplitude threshold levels.

Contact quotient (CQ), measured by electroglottogram (EGG), is a ratio which illustrates the duration of vocal fold contact during one vocal fold period. In the present study CQ(EGG) was calculated from a sustained vowel phonation in three different phonation types (breathy, normal, pressed) at three amplitude threshold levels (25%, 35%, 50%). CQ(EGG) values were compared with experts' perceptual evaluation of the firmness of phonation. The contact time of the vocal folds differed significantly between the different phonation types at all threshold levels (P < 0.01). Perceptual evaluation correlated best with CQ(EGG) at threshold levels 25% and 35%. The results of the linear regression model suggested that by using threshold level 25% the effect of F0 and SPL on CQ(EGG) were not significant.