As pastors begin planning to eventually re-open parishes for worship, there is a key fact that must be considered: singing and speaking are propellant activities.
Some studies suggest that speaking alone spreads droplets more than coughing:
Loudon and Roberts investigated the role of singing in the spread of tuberculosis and showed that the percentage of airborne droplet nuclei generated by singing is 6 times more than that emitted during normal talking and approximately equivalent to that released by coughing27. More recent work using advanced particle characterization techniques have yielded similar results21,28,29,30. Chao et al.28 used an interferometric imaging technique to obtain the size distribution of particles larger than 2 μm and found that counting aloud from 1 to 100 releases at least 6 times as many particles as an individual cough. Likewise, Morawska and coworkers21,29 reported that counting aloud for 10 seconds followed by 10 seconds of breathing, repeated over two minutes, releases half as many particles as 30 seconds of continual coughing, which in turn releases half as many particles as saying “aah” for 30 seconds. They also reported that more particles are released when speech is voiced, which involves vocal folds vibration, rather than whispered, which does not.
Much more here.
While surgical face masks do seem to be effective in preventing the virus from spreading by aerosol, homemade masks will vary from this standard in many ways, and may not protect congregations.
While it does seem to be useful to scale the number of allowed congregants to the size of the building, it seems to me that either parishioners should be asked to speak or sing responses internally, or asked to sit farther apart than six feet, or be provided with surgical face masks–which is unlikely at this point but may become possible in the future.