I think the classical comparison is like standing next to a turbojet or a decent firecraker? Maybe just next to the muzzle of a very large calibur machine gun.

Its very very loud, and could be dangerous if the impulse/intensity wasn't so low. Last I read the duration of the high decibel sperm whale sounds were super short. Like, fractions of a second iirc.

And the whispering is probably true, but probably not out of concern for our well being. It's never a great idea to anthropomorphize an animal. Its more likely that it they dropped volume for a more practical reason. Maybe they just didn't need more detailed information after the high energy scan.