What is a sonic boom? Why was it in the news recently?
Sound travels in the form of waves which are emitted outwards from its source.
In air, the speed of these waves depends on a number of factors, such as the temperature of the air and altitude.
From a stationary source, such as a television set, sound waves travel outwards in concentric spheres of growing radii.
As long as the source of the sound keeps moving slower than the speed of sound itself, this source– say a truck or a plane, it remains nested within the sound waves that are travelling in all directions.
When an aircraft travels at supersonic speed – meaning faster than sound (>1225 kmph at sea level), the field of sound waves moves to the rear of the craft.
A stationary observer thus hears no sound when a supersonic flight approaches, since the sound waves are at the rear of the latter.
At such speeds, both newly created as well as old waves, are forced into a region at the aircraft’s rear called a ‘Mach cone’, which extends from the craft and intercepts the Earth in a hyperbola-shaped curve, and leaves a trail called the ‘boom carpet’.
The loud sound that is heard on the Earth when this happens is called a ‘sonic boom’.
When such aircraft fly at a low altitude, the sonic boom can become intense enough to cause glass to crack or cause health hazards. Overland supersonic flights have thus been banned in many countries.
Bengaluru residents heard a loud sound recently which puzzled lakhs of city dwellers.
It was revealed to have emanated from an IAF test flight involving a supersonic profile.
