F-104 going supersonic at something like 500ft or slightly lower within less than a mile feels like a full body slap which makes the parts of your clothing which are not tight flutter. Anything a few thousands feet up is still very loud but doesn't do the slapping and fluttering anymore. Anything a few 10.000 feet can still be very loud. Though it varies. Don't know on what it depends exactly. Had 4 in row making nice contrails high up, rather soft. Had single ones, also high up, making a contrail, banging loud and sharp, thinking why was that? Those are all memories from the 80ies. Can't remember when I heard the last supersonic boom anymore. Has to be early 90ies. Today I laugh when I read about people calling the emergency services when they heard one ;-)