Dispersion of speech aerosols in the context of physical distancing recommendations

TL;DR

This study uses high-speed imaging to measure how far speech aerosols travel at different sound levels, finding that 6 feet distancing is generally effective for initial exposure but may not prevent prolonged aerosol exposure.

Contribution

It provides quantitative analysis of aerosol dispersion during speech at various intensities, combining experimental data with classical jet scaling laws to assess physical distancing effectiveness.

Findings

6 feet distancing likely prevents initial aerosol exposure

Loud speech aerosols travel similar distances as coughing

Prolonged exposure may occur beyond initial penetration

Abstract

High-speed particle image velocimetry (PIV) was used to quantify the dispersion of aerosol-laden gas clouds generated during phonetic vocalization by a human subject at different sound intensity levels. The measured PIV data was used to quantify the initial penetration depth. Using classical pulsed jet scaling laws propagation distances were computed for time periods beyond the measured duration. Our results indicate that the penetration distance was comparable between loud intensity speech (for example during singing, classroom lectures, parties etc.) and moderate intensity cough. Based on theoretical aerosol propagation distance and time, the 6 feet physical distancing recommendations are likely sufficient to avoid incidental exposure by the initial penetration of the aerosol cloud, but insufficient for prolonged exposure to slow propagating aerosol clouds.