Abstract:

Speech intelligibility is an important acoustic index for the acoustic environment quality in speech purpose halls. Long reverberation time (RT) and high background noise level (BNL) can reduce speech intelligibility in rooms. There have been numerous reports on the research of acoustic environment in university classrooms, but there are few studies on the acoustic environment in experimental teaching rooms in universities. Objective acoustic measurements were conducted on 14 physics experimental teaching rooms at a university in Guangzhou to obtain objective acoustic parameters, such as BNL, Early Decay Time (EDT), RT, Early Late Sound Energy Ratio (C50), and Speech Transmission Index (STI). Its aim is to study and analyze the acoustic environment of these experimental teaching rooms. The results showed that the average BNL in the empty experimental teaching rooms was 37.1 dBA, and the average BNL during experiments increased to 57.9 dBA. In these experimental teaching rooms, the average values of EDT, RT, C50, and STI were 1.23 s, 1.26 s, -1.89 dB, and 0.54, respectively. Comparative testing shows that under the same spatial dimension conditions, the RT in experimental teaching room is shorter than that of conventional classrooms, and the frequency characteristics of RT in experimental teaching room change relatively smoothly; This work has also found that large laboratory tables with cavities can help reduce RT in experimental teaching rooms and improve the frequency characteristics of RT in experimental teaching rooms. Further analyzed results shows that among the 14 experimental teaching classrooms tested, the objective acoustic parameter results of 13 experimental teaching classrooms are lower than the recommended values of existing relevant specifications and codes. It is recommended to take appropriate acoustic treatment measures to reduce RT and BNL to improve acoustic environment in these experimental teaching rooms. This helps to enhance the speech intelligibility in experimental teaching rooms, to make their acoustic environment meet the needs of university experimental teaching and to ensure a good voice communication environment between teachers and students.

Key words: experimental teaching classroom, background noise level, reverberation time, speech intelligibility