Speed of an object such as missile moving through any media like air, or water compared to speed of sound at certain physical conditions is measured in Mach. 1Mach is equal to speed of sound. 2 Mach is double than the speed of sound. Speed more than a Mach but less than 5 Mach is called supersonic. Speed less than 1 Mach is called Subsonic. The speed between 0.8 to 1.2 Mach is also referred to sometimes as Transonic. A speed more than 5 Mach but less than 10 Mach is called Hypersonic. An object moving at speed of more than 10 Mach is called High-hypersonic. India’s BrahMos is a Supersonic Cruise Missile.