What is Sonic boom?

Sonic boom is the loud noise created by the shock wave set up by an aircraft travelling at a speed faster than that of sound. Any plane in flight produces disturbances in the air through which it moves. As a result, pressure waves move out from points on the craft’s surface in much the same way as ripples spread out when a boat moves through water. These waves travel at the speed of sound and spread out ahead of the aircraft. If the plane travels at a subsonic speed the path ahead of the plane is cleared for it, so to say, and it never catches up with the pressure disturbance. However, at sonic speeds the sound waves and the aircraft are both travelling at the same speed and the waves cannot move ahead. As a result they pile up, reinforcing one another and this creates a high pressure shock wave, which causes the sonic boom.

The intensity of the sonic boom depends not only on the speed of the aircraft but also on the altitude at which it is cruising. The boom becomes less intense as the plane gains altitude.

Since the shock waves from a sonic boom can damage buildings, planes like the Concorde are not allowed to travel at supersonic speeds when flying over cities.