Thanks for the info, I've got some more reading to do..Airborne acoustic anomalies are more easily controlled through changing the configuration of the source (the aircraft) itself. e.g. A hypersonic biplane reduces the acoustic signature dramatically over a mono-plane configuration because it creates wave cancellation and disruptor effects. You also get interesting compressive lift qualities from a biplane. There is plenty of open source information on supersonic biplanes.
The Return of the Supersonic Biplane - Popular Mechanics
cheers
w
It would seem to be a pretty big development going to a completely hypersonic plane with hypersonic weapons. I would assume the biggest risk of the project is not technical but budgetary?