I use Aguila 22 ammo at times, quieter than a pellet gun. My favorite is the 500 fps ammo, the 375 fps ammo is to weak for most shooting except plinking with kids in the back yard.
I have dispatched a possom & piegons(sp?) with the 500 fps ammo. I usually mail order from Midwayusa. I also have some 22 WRF ammo to shoot in 22 magnum guns, it's slower than most 22 lr ammo. It has normal sound but really tames the 22 magnum.