Hedonism Bot
It depends on the gun. I use this ammo called Aguila Super Collibiri in my .22 rifle (not sopposed to aparantly but i do anyway), and that is wayyyyyy quieter than my .177 air rifle

Tyler N
i have a .177 gamo and it is way quieter than a .22cal

Mark
The .22 caliber pellet requires more air to move it down the barrel, so you'll hear a slightly louder "pop" as that pellet leaves the muzzle over the .177 caliber pellet.

BENJAMIN L
not much of a difference but id say 177 is slightly quieter!

C_F_45
It's the same make & model rifle with the exact same powerplant, the only difference is the barrel. You would not be able to tell any difference*, unless you use ultra light weight pellets** in the .177 *Maybe with a hyper-sensitive electronic listening device they might be able to pick up a very slight difference in sound. **Pellets such as the Gamo PBA Raptor or Crosman Silver Eagle will break the sound barrier. Gamo Whisper .177 or .22 The specs, except for the >claimed "up to"< MV are identical