If the can is a decient quality , with sub sonic ammo it shoulden't be any louder than the weaker pellet rifles , I've shot sub sonic 308 through several good cans and the firing pin noise is clearly noticable , the report from the gas leaving the can is not as loud as breaking the quick connect fitting on an air line with a very short hose , kinda like a "pffft". I'm sure that the Whisper woulden't be louder than the sub sonic 308 as long as its sub sonic.
even with full hous 308 ammo through a good can is not as loud as a bolt action 22 long rifle with standard speed ammo , completly safe to shoot without hearing protection.
What model is your 30 can can?
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