Classroom noise exposure and evaluation of an acoustic intervention among Chinese students

Excessive classroom noise is an important, but under-addressed, environmental health concern in schools, with potential implications for students' listening conditions, learning, and hearing health. This study examined classroom noise exposure among Chinese students and evaluated whether a Classroom-oriented Distributed Acoustic Equalization Intervention (C-DAEI) improved classroom acoustics, speech intelligibility, and hearing-related outcomes. The study combined large-scale cross-sectional surveillance with a six-month cluster-randomized, parallel-group field intervention. Surveillance data from 398,629 students selected through stratified cluster sampling between 2019 and 2023 were used to assess classroom indoor noise across school settings. The intervention included 295 students and compared classrooms equipped with C-DAEI with classrooms using standard sound reinforcement. Outcomes included standardized acoustic indicators, speech intelligibility, and pure-tone audiometry in a symptomatic subsample. Nearly half of student-linked classrooms exceeded national noise limits, with non-compliance more frequent in urban than rural schools. Compared with standard sound reinforcement, C-DAEI improved sound-field uniformity and speech transmission conditions. Students in the intervention group achieved higher post-intervention speech accuracy than controls. Audiometric changes were modest, but hearing thresholds showed favourable trends. These findings suggest that optimized classroom sound reinforcement may be a practical school-based strategy for improving listening environments and supporting hearing health.