That's exactly right! Shock waves are the primary reason you hear what's
called a sonic boom. But there's more to a sonic boom than just shock
waves. Here are the basics:
object moving at supersonic speed (airplane)
medium through which sound can travel (air)
Picture an airplane flying through the air. As the airplane moves, it pushes
air molecules out of its way, continuously creating waves of compressed and
uncompressed air. These air pressure waves move away from the airplane in all
directions at the speed of sound. (Imagine ripples that form by dropping
a pebble in a pond.)
Next, break the sound barrier by increasing the airplane's speed to
supersonic, or faster than the speed of sound. When the airplane moves at
supersonic speeds, the air pressure waves begin to pile up ahead of the
airplane and compress, forming shock waves. (These are similar to a "bow
wave" that piles up at the front of a boat as it moves through water.)
The shock waves will move out and back from the plane, towards the ground.
There is a sudden change in pressure when the shock wave hits your eardrum. You
hear this as a loud sonic boom.
To increase the intensity of a sonic boom, increase the size of the airplane.
The larger the aircraft, the more air it displaces and the stronger the shock
waves become. Also, the lower the altitude of the plane to the ground, the more
intense the boom will be. That's because the shock waves will have less
distance to travel before hitting the ground, and they will have lost less
energy. Note: other factors influence the intensity of a sonic boom, including aircraft shape
and outside air temperature and pressure.
To reduce the intensity of a sonic boom, decrease the size of the plane
and increase the flying altitude.
Think you understand sonic booms? Try this challenge and see.