I recall, actually, a Harrier being EXTREMELY loud.
But, the loudest I recall (and admittedly, it might have been partially due to the WOW factor) was an SR-71 taking off from Edwards AFB, about 100 meters from where I stood.
Ditto on the Harrier being one of the loudest military jets I’ve ever heard.
As for the quietest, it just might have been the F-117. Although I don’t especially remember what it sounded like, being more agape at the sight of Batman’s plane flying overhead.