Abstract
Speech intelligibility in classrooms, determined by signal-to-noise ratio and room acoustics quality, is important for communication between teachers and students. This work reports on the current situation of speech intelligibility evaluated using useful-to-detrimental ratio (U50) in 12 unoccupied classrooms near roads. To examine the influence of traffic noise transmitted into classrooms on the speech intelligibility, on-site measurements were carried out according to closed and open window conditions. The results showed that the average U50 values were 2.68 ㏈ and –3.73 ㏈ for closed and open window conditions, respectively, indicating the importance of background noise control in classrooms. Based on the measured U50 values and the precedent study, proper background noise levels in classrooms in case of an open window were 43.3 ㏈A and 47.8 ㏈A to meet the minimum level for a “good” class (USUB50/SUB = 1.5 ㏈) and the middle level for a “fair” class (USUB50/SUB = –1.0 ㏈).
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