Emission rates, size distributions, and generation mechanism of oral respiratory droplets

Large Particle Emissions from Human Vocalization and Playing of Wind Instruments

“…Johnson et al conducted similar large particle emission quantification experiments for talking with 8 participants but produced quite different results, finding a substantial mode for large particle emissions at 145 μm, which we did not find in this study. Similarly, Harrison et al also found no evidence for a secondary mode of large particle emissions around 145 μm. They also reported insignificant differences for count emissions between their talking and singing groups and showed large interparticipant variability between these groups.…”

“…Data on spot count, size, and location were imported into R, version 4.0.2 (), for further analysis. A spread-factor equation d p = 1.364 e − 5 d s + 0.4443 d s − 1.4758 was used to convert spot diameter ( d s ) to aerodynamic particle diameter ( d p ) at the time of impact, following the calibration provided by Harrison et al To estimate the original emitted particle diameters, we modeled the change in diameter between the point of release and WSP contact using a deterministic model (2.5 ms time steps) based on the rate of particle evaporation d false( d normalp false) d t = 4 D M R ρ p d p true( P normalg T normalg − P normald T normald true) and particle settling V T S = ρ p d normalp 2 g C c 18 η where d p is the particle aerodynamic diameter, D is the molecular diffusivity of water vapor in air at 293 K, M is the molecular weight o...…”

“…Several previous studies have sought to characterize the full spectrum of aerosol sizes, ,,− but these experiments were limited by small sample sizes ( n < 12) and mainly focused on emissions from talking with little variation in the type of speech and articulation investigated. A recent study by Harrison et al utilized a larger cohort of participants to investigate large particle emissions from speech ( n = 43) and singing ( n = 26) but did not consider emissions from any musical instruments or the effect of face coverings. The objective of this work was to characterize large respiratory aerosol (35 < d p < 100 μm) and droplet ( d p > 100 μm) emissions from a panel of individuals ( n = 70) of varying age and sex while talking, singing, and playing various wind instruments.…”

“…The COVID-19 pandemic has motivated a growing body of research on human respiratory aerosol generation and disease transmission associated with activities like talking, singing, and playing musical instruments. − To date, most of this research has focused on smaller particles (aerodynamic particle diameter, d p < 10 μm), which are relatively easy to count and size using conventional instruments like optical particle counters and aerodynamic particle sizers . Smaller particles are important because they can remain airborne for hours and travel distances beyond typical “close-contact” thresholds used in disease control guidance (∼2 m) and have been shown to transmit infectious pathogens in air. , However, larger particles ( d p > 10 μm) are also emitted during the same respiratory aerosol generation processes.…”

“…was used to convert spot diameter (d s ) to aerodynamic particle diameter (d p ) at the time of impact, following the calibration provided by Harrison et al 5 To estimate the original emitted particle diameters, we modeled the change in diameter between the point of release and WSP contact using a deterministic model (2.5 ms time steps) based on the rate of particle evaporation i k j j j j j j y…”