Look for .22LR bullets with only about 700 feet per second velocity
CCI makes the .22LR called quiet , I think it is called.
Another choice is Aguila .22 colibri, no gun powder but shoots about 420 fps.
Not supposed to use in rifles because they say bullets can stick in barrel, but I have never had that happen.
Very quiet, only uses primer to shoot.
Probably won't cycle a semiautomatic.