Investigation of acoustic comfort, productivity, and engagement in naturally ventilated university classrooms: Role of background noise and students’ noise sensitivity

Optimal classroom acoustics enhance students' engagement and learning efficiency. In warm-humid climate, ceiling fans are used at different speeds to enhance thermal comfort in naturally ventilated classrooms. Although ceiling fans enhance thermal comfort, using fans at higher speeds significantly increases Background Noise (BGN), interfering with acoustic comfort. To achieve an optimal acoustic environment, it is important to understand the effect of BGN on acoustic comfort. Hence, focusing on ceiling fan noise in classrooms, this study investigates the effect of acoustic environment and students' noise sensitivity on acoustic comfort, productivity, and engagement. A four-month-long field study was conducted in 11 naturally ventilated classrooms, obtaining 828 responses. Sound pressure levels in active classrooms were measured to calculate BGN and Signal-to-noise ratio (SNR). Reverberation time (RT) was measured both in students' presence and absence. Acoustic comfort conditions, productivity, and engagement of students at every seat were obtained through questionnaire survey. BGN levels and RT ranged from 58.2 to 65.3 dBA and 0.7–2.1 s, respectively. A positive correlation was found between acoustic comfort and engagement level and productivity. Regression analysis showed that students with high noise sensitivity reported acoustic discomfort when the BGN exceeded 62.4 dBA, RT was above 1.7 s and SNR was below 3.7 dBA. Chi-square test involving the acceptability vote indicated that students were more likely to accept the BGN ≤61 dBA, RT ≤ 0.7 s, and SNR ≥6.5 dBA. This study establishes the relation of BGN, RT, and SNR with acoustic comfort in naturally ventilated classrooms, offering insights for classroom acoustic environment enhancement.