That's a very valid thought process, and is why I had a 590A1 next to my bed for many years. However I wonder how the chamber pressure correlates to sound pressure levels (SPL)? According to
this, a 18.5" 12 gauge registers 161.5db, a 18.5" .223 rifle registers 155.5db, and a 9mm handgun (presumably 4" barrel) registers 159.8db.
For me at least, my perception of the various volumes of firearms is largely impacted by the fact that I don't think I've ever discharged a shotgun indoors, but I have shot plenty of rifle and handgun at indoor ranges. And 5.56mm indoors rocks your socks, I won't even do it unsuppressed anymore. However shooting clays with my 28" Browning, I almost feel like hearing protection is unneeded (I know it is, and I wear it, but its such an enjoyable, quiet experience). But looking at the numbers doesn't seem to support that 12 gauge shotguns are quieter than rifles or handguns, all things equal.