Can confirm CBees are about at loud as a pellet gun when fired from a 20” 22lr. Colibri are even quieter I use them for tree rats getting at my bird feeder they fully penetrate a treerat in the boiler room at 20 feet. They are so quiet they make a little pook sound. 20gr at 500 fps is twice the KE of a 177 pellet at 700 fps
https://www.academy.com/shop/pdp/aguila-ammunition-super-colibri-22-20-grain-rimfire-ammunition
I remember, years ago, a guy at the LGS demonstrating the colibris in the shop. I used to fight getting CB Longs into the 10-22 chamber. I was ecstatic when a LR option came out. The frangible HP was icing on the cake.