If you've read the July 2004 issue of
Popular Science, there was a long article on how a modified Northrop F-5E succeeded in reducing the pressure wave around the plane that creates the sonic boom. In short, they have proved it is now possible to drastically reduce the intensity of the sonic boom so people on the ground will either barely hear it or not hear it at all.
This will now pave the way for a supersonic transport of the future that could fly in a few years. I'm sure Gulfstream Aerospace (who has been studying a supersonic business jet since the late 1990's) could be on the verge of announcing such a plane.
Imagine being able to fly from JFK to London area airports at Mach 1.7-1.8 but with no sonic boom audiable on the ground and also much lower noise and exhaust emissions.