Why does my airgun shoot quieter than a firearm?

Airguns release a smaller volume of gas at much lower pressure than a centerfire firearm (a few thousand PSI vs tens of thousands), and they have no powder combustion to amplify the report.

The remaining noise is the pellet's mechanical departure plus, on a springer, the spring/piston's vibration. Shrouded barrels, factory moderators, and integrated suppressors on PCPs and some break barrels reduce that further. Always check local law: airgun moderators are perfectly legal in most US states but a few states regulate them like firearm suppressors.