Evaluation of Noise Levels and Speech Intelligibility in a Classroom under Different Air Conditioner and Air Purifier Operational Conditions

The use of air quality systems in school classrooms has grown to enhance the indoor environment and reduce the spread of airborne infections. However, this has resulted in increased noise levels and reduced speech intelligibility during classes. This study examined noise levels and the STI in a classroom, focusing on the operational conditions of an air conditioner and an air purifier. Strategies for achieving optimal speech intelligibility under different operational scenarios were evaluated using acoustic simulations in a typical classroom setting. The findings revealed that reducing reverberation time did not always improve speech intelligibility due to the elevated noise levels generated by the equipment. The minimum noise level produced by the equipment was approximately 36 dBA. Considering the practical constraints of developing low-noise devices, an alternative approach is to increase the speech level to achieve a signal-to-noise ratio (SNR) of at least 10 dBA. Additionally, positioning the equipment at the front of the classroom, near the speaker, proved beneficial for ensuring a uniform distribution of speech intelligibility across all listening areas.