Sonic flight without the boom

Hello all,

I have heard of a way to attenuate the sonic boom on ground by keeping the
shockwaves along the jet flight line. This way, the shockwaves are not
attenuated when they are emitted from the aircraft, but they are when they
reach the ground because they are farther from their emitting point than in
a classic supersonic jet.
But I do not know if this is what NASA perform with its tests.

--
Paul