Acoustical transmission of face coverings used to reduce coronavirus transmission in a classroom environment

Abstract

The COVID-19 pandemic has caused many communities to require the wearing of face coverings, masks, and/or shields indoors to reduce the transmission rate of the virus, which includes educators and students in classroom settings. Several types of face coverings are studied, including standardized N95 and KN95, assorted cloth, and clear plastic face shields. They are evaluated on an acoustical head and torso simulator (HATS) setup in a classroom with two different locations for monitoring via a sound level meter. The HATS is used as a controlled and repeatable artificial voice or sound source, which creates white noise, artificial speech, and real speech signals. Sound levels throughout the classroom are measured to determine the direct field and reverberant field regions, and they are compared to a room acoustics model. Attenuation at octave band frequencies due to the face coverings are evaluated at a location of 2.0 m from the HATS, which is within the direct field to reduce the room acoustical effects, with evaluations repeated at a location near the back of the classroom (6.2 m) to include those room acoustical effects. The acoustic effects of the face coverings are compared to reported droplet transmission rates.