Experimental characterization of speech aerosol dispersion dynamics

Area of Science:

• Aerosol science
• Fluid dynamics
• Infectious disease transmission

Background:

• Airborne diseases, including SARS-CoV-2, spread primarily through human aerosols.
• Non-symptomatic aerosol-producing activities like speaking are less understood than coughing or sneezing.
• Quantifying aerosol dispersion from vocalization is crucial for risk assessment.

Purpose of the Study:

• To quantify aerosol dispersion from human vocalization.
• To compare aerosol production and penetration rates of different syllables.
• To understand the fluid dynamics influencing aerosol plume behavior.

Main Methods:

• High-speed particle image velocimetry (PIV) was used to measure aerosol dispersion.
• Human subjects produced syllables with varying aerosol production rates.
• Aerosol penetration was compared between syllables and coughing.

Main Results:

• Aerosol production and penetration were found to be uncorrelated.
• The syllable 'ti' showed similar aerosol penetration to coughing, while 'ma' did not.
• Aerosol plumes exhibited a 'jet phase' followed by a 'puff phase', with vortex rings concentrating particles.

Conclusions:

• Vocalization aerosols can travel significant distances, comparable to coughs.
• Vortex ring structures play a key role in aerosol plume transport and dilution.
• Accurate exposure risk assessment requires considering aerosol production, penetration, direction, and airflow.