Sonic boom the ground. For example, the speed of sound at is about , but an aircraft must travel at least (Mach 1.12, where Mach 1 equals the speed of sound) for a boom to be heard on the ground. The composition of the atmosphere is also a factor. Temperature variations, humidity, atmospheric pollution, and winds can all have an effect on how a sonic boom is perceived on the ground. Even the ground itself can influence the sound of a sonic boom. Hard surfaces such as concrete, pavement, and large buildings can cause reflections which may amplify the sound of a
Shock wave be: Some other terms The abruptness of change in the features of the medium, that characterize shock waves, can be viewed as a phase transition: the pressure-time diagram of a supersonic object propagating shows how the transition induced by a shock wave is analogous to a "dynamic phase transition". When an object (or disturbance) moves faster than the information can propagate into the surrounding fluid, then the fluid near the disturbance cannot react or "get out of the way" before the disturbance arrives. In a shock wave the properties of the fluid (density, pressure, temperature, flow velocity, Mach number) change