Half Moon in Evening Sky Over Flame Trench, Launch Pad 39B, Kennedy Space Center, October 2015
The sound power of a launching rocket is the result of the mechanical energy of the rocket's exhaust plume, which is defined by the thrust of the rocket times its exit velocity independent of the fuel and oxidizer being used.
Saturn V Launch Thrust - 7.6 million pounds
Space Shuttle Launch Thrust - 7.8 million pounds
Space Launch System Thrust - estimated 9 million pounds
Saturn V sound power - about 200 decibels
Space Shuttle sound power - about 160 decibels
Space Launch System - estimated in excess of 200 decibels
Permanent hearing loss in humans - approx 150 db
At launch, hundreds of thousands of gallons of water flood the main flame trench and pad surface to cool the structures and to absorb and re-direct shock waves and reduce sound levels.