Power Tower's four towers are powered by compressed air, high volume, low pressure. All movements involve opening/closing of valves/mufflers to facilitate a desired function. The four screw type compressors take a huge building under the safety/trim brakes of Corkscrew, they're quite loud, about as loud as the tower.
Skyhawk, the S&S Screamin' Swing uses air to swing both arms, the compressors are right next to Mine Ride's exit
Skyhawk is funband VERY loud.