Let's get loud: How classroom activities influence speech and noise levels during lessons

• Sound levels monitoring in 26 primary school classrooms during lessons. • Disentangling speech levels and activity noise through Gaussian Mixed Models. • Speech levels varied with activity type and declined with increasing students’ age. • Activity noise averaged 50 dB(A) in active classrooms. • Higher speech clarity (C₅₀) was associated with lower activity noise. Student activity noise is the dominant sound source in primary school classrooms. While it reflects the dynamic and interactive nature of learning, excessive noise can disrupt speech perception, impair concentration, and affect well-being. This study analysed the acoustic environment of 26 classrooms during real lessons, separating speech and activity noise using Gaussian Mixture Models. Ninety-three periods of homogeneous activities across Grades II–V were examined to assess the effects of activity type, student age, and classroom acoustic characteristics. Results indicated that the type of activity in the class is an important source of acoustic variability, with teacher-led lessons and group work producing the highest overall levels and quiet work the lowest. Activity noise averaged 50 dB(A) across activities, with large variability linked to class-specific behavioural dynamics, and speech levels were consistently higher in more interactive settings. Student age significantly affected speech levels, showing a nearly 5 dB decline from Grade II to Grade V, and, together with activity type, influenced the speech–noise relationship. Noise level analyses revealed a 10 dB increase from unoccupied to baseline conditions (occupied but inactive) and an additional rise of over 5 dB during activities. Classrooms with higher speech clarity had lower activity noise, highlighting the role of early reflections control in mitigating noise from student movement and interaction. The findings underscore the importance of integrating acoustic ergonomics into school design and refurbishment, through multidisciplinary collaboration, to support effective communication and learning—particularly for younger children.