"This test is unique because it's like going through the steps of a true launch, only on a much smaller scale. The noise the engines and boosters generate is so great that it can impact the rocket, and the crew, during liftoff. We have to ensure we have the proper suppression system to basically turn that noise down to a safe level."
Source: Jeremy Kenny, acoustics engineer at NASA's Marshall Space Flight Center in Huntsville, Alabama, describing tests in which a scale model of the Space Launch System (SLS), including solid rocket motors, was fired -- giving an "earful" of information about how low- and high-frequency sound waves will affect the rocket on the launch pad.