Okay with the Supersonic side of it, the pressure from sonic booms caused by aircraft often are a few pounds per square foot. A vehicle flying at greater altitude will generate lower pressures on the ground, because the shock wave reduces in intensity as it spreads out away from the vehicle, but the sonic booms are less affected by vehicle speed.
As to the Euro's checking out the chopper easiest way is to intercept at low-level and then slow down when you get near him. Also the RAF have to request Authorisation to go supersonic overland.
Also a Gazelle can carry quiet a bit of stuff that goes bang... so better getting to it quick than taking your time...