One version of Starship has also been proposed to be used for Earth to Earth transportation medium. It won't be anytime soon but when they become normal, how far would the human settlement have to be to not be bothered by sonic booms? Conversely, what could be the minimum distance of the launch/landing platform from the coastal city for it to not be bothersome for dwellers?
The only answer I can find is a NASA Facts sheet about sonic booms for aircraft "The width of the boom "carpet" beneath the aircraft is about one mile for each 1000 feet of altitude. An aircraft, for example, flying supersonic at 50,000 feet can produce a sonic boom cone about 50 miles wide"