White noise is the broad range of frequencies that can be picked up the psi people. It is used by the Department of Psi Youth to mainly control the children placed in Thurmond. It was the love child of a car alarm and dental drill and would be turned up high enough to make someone's ears bleed. Humans could not hear it, so it was used to subdue rebellion in psi living in the rehabilitation camps.
White noise was kept from most camps and kids from Thurmond were given two warning sounds before the white noise was released in a certain area. This system was probably introduced to help reduce injuries since the sound was so played so loud that it would almost instantly immobilize an entire group. The frequency most commonly used was probably closer on the orange side of things than green or blue since Ruby Daly was always sick after the noise was played, but the greens were able to return to normal within a few minutes.
Certain frequencies could be heard by one color. A couple of green frequencies sounds like a buzzing bee when it is played. The Children's League uses the knowledge and break into the rehabilitation camps to find reds, oranges and yellows hidden in the camps.
Clancy Gray was able to find a way that would allow him to play a message telling any psi listening where the location of East River.
The Camp Controllers tote around hand-held devices that can play the White Noise. The Children's League has smaller versions of these devices.