A genius in the realm of sound, Walter Shreeve built a suit to fully empower himself with the abilities of sound. But, once he showed it to Derek Powers, he went down the path of a true villain.
Using his genius and suit to its fullest, he's able to manipulate sound in almost any conceiveable way. He can amplify it into shockwaves, dampen so no sound can be heard, and even interfere with it so that no one can understand each other. Whatever the situtation, if sound is at play, Shriek is the one who's in control.