[Mastador1]

Or you could just a .22 cal. air rifle, probably no louder than a suppressed .22.

[yarddog]

I have an RWS Diana model 48 air rifle in .177 caliber. It shoots 1200fps with normal pellets.

I imagine it is louder than a suppressed .22 tho I don’t know that for a fact. It would do the job on any animal that size.