A lot of acoustic energy is produced by the exhaust of rockets. Shock waves are produced when the supersonic exhaust collides with the surrounding air. The rocket’s size and the velocity of the exhaust affect how loud these shock waves are. At close range, the loudness of large, high-performance rockets could cause death.

Around its base, the Space Shuttle made 180 dB of noise. NASA developed a sound suppression system that can pump water onto the launch pad at speeds of up to 900,000 gallons per minute (57 m3/s) to combat this. The water reduces the noise level from 180 dB to 142 dB, which is less than the design requirement of 145 dB. Without the sound suppression system, acoustic waves would reflect off the launch pad and into the rocket, vibrating the delicate payload and crew. The rocket may be damaged or destroyed by these powerful acoustic waves.

Because the engine noise radiates upward from the jet and also reflects off the ground, close proximity to the ground causes the most noise. Flame trenches with roofs, water injection around the jet, and deflecting the jet at an angle can all help reduce this noise.

For crewed rockets, a variety of techniques are used to lessen the amount of noise that the passengers hear, and most of the time, placing the astronauts far from the rocket engines makes a big difference. When a car goes supersonic, the sound stops for the passengers and crew because the sound waves can no longer keep up with the car.