OBJECTIVE: To assess the level of noise present in classrooms in public schools in Belo Horizonte, and to verify the perception of teachers about the noise and its influence on health. METHODS: Sixteen elementary school teachers (15 women 1 man) participated in this study. A questionnaire on vocal complaints and nuisance caused by noise at the school was administered to the participants. Measurements were performed in 18 classrooms to check the equivalent sound pressure level (Leq). Data analyses were performed using a Sound Level Meter, Microsoft Excel, and SPSS 16.0. RESULTS: The noise in the classroom ranged from 54.51 dB (A) to 70.37 dB (A). Therefore, all the rooms had assessed values above the acceptable limits stipulated in the regulatory standards (35dB (A)) (NBR 10152, ANSI S12.60). From the question it was ascertained that 75% of the teachers reported that the noise generated within the classroom causes a lot of interference and is a nuisance; 81.2% said they were forced to raise their voices during classes because of the existing noise, and 75% reported vocal fatigue due to the influence of the noise. The high noise level results in a vocal effort and can have negative consequences on the teacher's voice. CONCLUSION: Noise in classrooms disrupts school activities and has a major effect on the teacher's voice. Most teachers interviewed reported being very uncomfortable and exerting vocal effort during lessons, which can cause serious vocal damage. The noise found in classrooms is above the level set by regulatory standards.