PURPOSE: to check the maximum phonation time (MPT) of vowels and to correlate the results of the relations between /e/ voiceless and sound (ė/e ratio), s/z ratio and MPT obtained/predicted (MPTO/MPTP), according to the gender, ratio in future professional voice adults users with normal voice. METHOD: selection through the vocal evaluation by the RASATI scale; collection of MPT /a, i, u, e, s, z/, the /e/ voiceless and vital capacity; calculation of the s/z, ė/e, and MPTO/MPTP ratio of 50 women (average 21,42 years old) and 12 men (average 24,25 years old). RESULTS: in both sexes, the MPT were significantly inside or below the normality, suggesting balance or air escape during the phonation. The s/z ratio significantly normal, ė/e ratio significantly increased when compared to the reduce results, and MPTO/MPTP ratio without significant differences. It showed balance or hyper of vocal folds during the phonation. Significant positive correlation between the s/z and ė/e ratio, showing that they grow proportionally and what the MPTO/MPTP ratio does, is not correlated with them. CONCLUSION: the future professional voice adults users with normal voice studied presented the MPT of vowels inside or below the normality, the s/z ratio normal and the ė/e ratio above the normality, when compared to the group with decreased values, suggesting pneumo-phono-articulatory incoordination. The positive correlation between the s/z and ė/e ratio suggests that both supply compatible results, but it doesn't occur the same with the MPTO/MPTP ratio.