Study on an evaluation method of virus exposure risk by droplets focusing on a sound environment

The final goal of our study is to propose a new method to evaluate the risk of virus infection from the aspect of the sound environment. In this study, we attempted to quantitatively grasp the relationship between speech level and number of droplets when talking while eating at a restaurant. A psychoacoustic experiment was conducted in which the subject was made to speak under the condition that the background noise level was varied every 5 dB from 55 dB to 70 dB using a pair of speaker and listener as subject. From the results, the effect of background noise level on speech level was examined, and the relationship between speech level and number of droplets was clarified. Although the speech level tended to increase with increase in the background noise level, in the background noise range of 55 dB to 70 dB, there was no significant difference in the number of droplets with particle sizes larger than 100 μm. Furthermore, we evaluated the risk of virus exposure in droplet infection focusing on the indoor background noise level.