[kach22i]

NASA opens new chapter in supersonic flight
http://spaceflightnow.com/news/n0309/06supersonic/

Flight tests completed by NASA, with government and industry partners, may have demonstrated a way to reduce the window-rattling impact of sonic booms.........................................An aircraft traveling through the atmosphere continuously produces air-pressure waves similar to waves created by the bow of a ship. When the aircraft exceeds the speed of sound (approximately 750 mph at sea level), the pressure waves merge to form shock waves, which are heard as a sonic boom, when they reach the ground. The flight tests showed by designing the aircraft to a specific shape, the pressure waves can be kept from merging. When these weaker waves reach the ground, the loudness of the sonic boom is greatly reduced.

Credit: NASA


Interesting comments by Craig Fink:
http://www.usenet.com/newsgroups/sci.aeronautics/msg00104.html