Why do some rockets make a smooth, continuous “woosh” sound while others make a rougher popping/rumbling sound?

Question

Why do some rockets make a smooth, continuous “woosh” sound while others make a rougher popping/rumbling sound?

In: 1

Answer 1

Generally rockets with solid rocket boosters sound a lot rougher and poppier than rockets that only use liquid fuelled engines.

That is because SRBs use propellant that is made up of grains in a binder and as each grain burns it creates a flare of noise which overlaps with all the other grains burning.

In a liquid propellant engine there are droplets of fuel burning but they are much smaller than the grains in solid propellant so the noise is smoother.

Rockets with big SRBs such as the Space Shuttle and SLS create more noise than those with smaller SRBs such as Atlas V and Vulcan. The quietest rockets for their thrust are the Falcon 9 and Falcon Heavy but they are still plenty loud.