The main objective in a classroom is clear communication between teacher and students, which is directly influenced by the architecture of the classroom or internal and external noise. Background noise, such as air conditioning, babbling or traffic noises coming from outside, can decrease the speech intelligibility in the room and the students' attention. The aim of this paper is to analyse how different background noise sources can influence students' attention and information retention ability. For this purpose, a classroom is simulated and auralised with different background noise sources. The sound pressure level inside the classroom will remain the same according to the Brazilian standard ABNT NBR 10.151 (2019) for the different sources. The influence of this background noise is evaluated according to the users' performance in a listening test using the serial recall method.