Exploring sound diffusion in learning environments through experimental and wave-based analysis

Acoustic design guidelines in learning environments generally involve specific requirements of reverberation time (T20), speech clarity (C50), and speech transmission index (STI) to ensure adequate quality for spoken communication. Predictive formulas recommended by international standards rely on ideal diffuse field theory as a crucial factor for meeting adequate room acoustics criteria. However, such theoretical assumptions are barely encountered in real-world rooms, undermining the predictions' accuracy. The present work explores the main factors influencing sound diffusion in classrooms by means of in-field acoustic measurements and numerical models. In detail, different desk configurations and the installation of materials with varying acoustic impedances at the suspended ceiling have been studied to evaluate the associated increase in sound diffusion. Among the several metrics to quantify sound diffusion, the standard deviation of measured reverberation time values has been selected in the present study. Experimental and simulated data findings reveal that the furniture layout with a single desk arrangement and the suspended ceiling's treatment with porous and perforated ceiling tiles increase sound diffusion by exploiting edge diffraction and material discontinuities, respectively.