So it still has a sonic boom, just not heard on the ground??? Any current aero-engineers that can explain this further? Is it simply because the incident angle of the wave is so shallow it extends over the horizon rather than intersects the Earths surface?
I’m not an aerospace guy but IIRC the angle of the mach lines increases with speed until you hit the speed of sound at which point the angle stays constant. So you can’t avoid an audible boom on the ground by narrowing the mach cone.
I’m guessing they’re softening the boom by spreading out the energy of the pressure wave. The long pointy nose displaces air in a relatively gradual way compared to a blunter nose. The result is a waveform with more duration but less intensity which is perceived by the ear as softer.