How to reduce the noise of the supersonic passage(bang)?
Most supersonic aircraft have points where the cross-section suddenly changes, such as the fuselage nose, the wing root leading edge or the wing trailing edge. The points of sudden change produce sharp changes in air pressure, i.e. loud sonic booms. Concorde was one example.

By designing the plane's cross-section to vary smoothly from end to end, the handful of points of major change are replaced by many more points of minor change. The booms are thus reduced in loudness and spread out in time, making them less intrusive.

Other factors which help include overall aerodynamic efficiency, light weight and high cruise altitude. A small, carefully-profiled and aerodynamically modern high-flying aircraft can thus be a lot quieter.