you are technically exceeding MACH ONE when your airspeed indicator/machmeter is exceeding mach one.
you are going fast, congratulations...but the air around the plane )or speed probes( is not supersonic. you are reading .85 mach...you aren't making a sonic boom
if you are civilian. there are few ways to exceed mach one. concord, concordski, DC8 on one flight over edwards, and a few lucky ride alongs in military planes are it.