A SONIC Boom was heard over London and Cambridge in January 2021 leaving millions confused by the loud bang.
But what is a sonic boom and what causes it?
What is a sonic boom?
A sonic boom is the noise created by the shock waves created when a flying object travels faster than the speed of sound.
They sound like a loud explosion or thunderclap that can cause minor damage to buildings and wake sleeping people.
The speed of sound, known as Mach 1 for aircraft, is approximately 767mph at sea level.
The noise of a sonic boom isn’t heard in all directions from the object and isn’t only heard at the moment the object crosses the speed of sound.
The boom is a continuous effect that is created while the vehicle is travelling at supersonic speeds.
What causes a sonic boom?
As an aircraft passes through the air it creates a number of pressure waves both in front and behind it, in the same way a boat creates waves at its front and back as it passes through the water.
Those waves created by the plane travel at the speed of sound and when the object goes faster than the speed of sound those waves are forced together because they cannot get out of the way fast enough.
They then form a single shock wave which creates a vapour cone with the aircraft at its tip.
There is a rise in pressure at the nose which decreases to a negative pressure at the tail.
The sound of the boom is experienced when there is a sudden change of pressure.
A “double boom” is created – one from the initial pressure created and then another when the pressure returns to normal.
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