What is a Sonic Boom?

‘Sonic Boom’ is the sound associated with the shock waves created by an object travelling through air faster than the speed of sound.

Perhaps the easiest way to visualize what is happening is to look at an object moving through a more viscous material than air – let’s use water for our example. As an object, such as a boat moves through water at a slow speed, it creates ripples on the surface – waves. The faster the boat goes; it starts to catch up with and overtake the waves it is creating and it creates a ‘wake’ which is a much larger single wave formed by all the small waves added together.

It’s the same for objects moving through air – as they move (much faster as air is not as dense as water) they produce sound waves by changing the air pressure all around them. As they start to approach then overtake the waves they have created, a single much larger sound wave is created – the sonic wake or ‘Boom’ This happens when the speeding object travels at around 340m/s or 700mph

So just like being on the shore of a lake as a speedboat goes past, covering you with its wake – if an object files past you faster than the speed of sound you will be hit with its sonic wake.

And just like boats, where the bigger the boat, the bigger the wake – it’s the same for objects moving through air. If you are unlucky enough to have a sniper shooting at you with supersonic rounds, you will hear the crack of the bullet as it hopefully misses its target, passing you by! but much louder than this is the sonic boom created by an aeroplane passing overhead.

The loudest sonic boom you could expect to encounter was created by Concorde travelling at Mach 2 (twice the speed of sound) due to its large size and relatively low altitude of flight, followed by the Space Shuttle on landing approach, and finally the SR-71 blackbird, however all three of these supersonic craft have been retired from service, therefore these days we are only likely to encounter much smaller sonic booms from fighter aircraft, or supersonic bullets.

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