I found this:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/
but it only speaks to health care workers.
There is also this https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3591312/
(regarding surgical masks).
Surgical masks are quite similar to a multi-layered cloth mask (surgical masks are certainly not n95 rated by any stretch of the imagination). There are sources for n95 cloth material and other filter material that can be placed into the cloth masks (mine all have pockets for filter material). It looks like about a 3.4% reduction of virus transmitting particles of numerous sizes is seen in the studies that have been done that I am able to find with a quick search. I'm still looking for the one that talks about in home setting and a roughly 10-20% reduction in transmission from an infected individual (familial caregivers not getting sick while caring for an infectious family member).
The point is if masks are ineffective with health care workers who k is how to fit and wear them they are even more useless in the general public. I firmly believe masks make it worse. Joe sox pack goes into the grocery store wearing the same mask that has been in his car for a month. It is loaded with bacteria and respiratory secretions. While in the store he adjusts the mask multiple times and then touches other surfaces with his contaminated hands. done in the store? the mask with his cooties plus the other cooties he picked up touching things in the store goes in his pocket or glove box etc to marinate until the next use....