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)
  
• shock waves
  
  

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.