Comparison of the reverberation time and speech transmission index (STI) in classrooms built in different decades

Abstract

This study compares and evaluates the reverberation times (RT) measured in two classroom buildings at the Federal University of Paraná, which were built in different decades. The RT of each room was measured according to the ISO/3382-1 standard. This paper presents simulations of RT and the speech transmission index (STI). In the simulations performed with the software ODEON, the influence of different materials on those indexes is analyzed. For one of the classrooms in the BG building, whose measured mean RT was 2.5 s, the simulations indicated the need to replace some of the finishing materials, especially on the floor and ceiling, for others with greater sound absorption coefficient. Results of the simulations pointed to a reduction in almost 2 s in RT. With respect to STI, the initial situation pointed to values between 0.39 and 0.42, which meant that intelligibility was poor, according to limits set by the IEC 60268-16 standard. The reduction in RT led STI values to range between 0.73 and 0.76, rendering intelligibility as good, according to the IEC 60268-16 standard.