Years ago, I shot a suppressed M3 "Grease Gun" in a side match at a big
bowling pin shoot. The suppressor looked like an old design but it
worked well. When the gun was fired I heard the
230 grain FMJ .45s hitting the steel targets set up 15 yards downrange.
Not much else.

The shoot organizer also had a suppressed .50 cal rifle (made on a
German Anti-tank rifle.) It was so quiet we could stand around
without ear protection while he fired it.

Tried a .22 suppressor (owned by an MG dealer) more recently.
With CCI Quiet .22 the slap on the target board was louder than the
report of firing a round. The suppressor was pretty basic but worked
anyhow.