PURPOSE: To explore the existence of correlations between environmental noise in classrooms, voice intensity and teacher's vocal problems. METHODS: Environmental noise was measured in 10 classrooms of municipal elementary schools; the intensity of teachers' voice was measured during teaching practice; teachers' speech samples containing emissions of sustained vowel [é] and counting from 1 to 20 were analyzed using the GRBASI protocol; and the results were tested for correlation. RESULTS: The average of environmental noise varied from 40 to 51 dB(A) without the presence of children in the classroom, and from 45 to 65 dB(A) with the presence of children. Among teachers, there was 70% of vocal problems (G) and 90% of vocal strain (S) varying from moderate to mild degrees. The intensity of teachers' voice varied from 52 dB(A) to 68 dB(A), reaching 7.48 dB(A) above the environmental noise. There was a significant correlation between the intensity of teachers' voice and the environmental noise during the class in the presence of children. CONCLUSION: There were high levels of environmental noise in the classrooms, which correlated with the intensity of teachers' voice (SPL). Although there was high occurrence of vocal problems in this sample, they were not correlated with the level of environmental noise.