A phenomenon long known but little understood by humans is what is termed poltergeist, or ghost knocking. Researchers have correctly identified that it is not caused by spirits but by the living. Is this a deliberate act? Most definitely, and the fastest way to locate the perpetrator is to scan for the angriest person, as intense rage is the engine by which poltergeist activity is run. Intense and unremitting anger sets the brain into Theta waves, and this builds over time until another offshoot is possible. What humans take to be their physical surroundings are what they can see, hear, feel, and observe to have substance as it moves, has color, or has a physical effect that can be observed. Humans understand that air is a substance as the action of wind is felt and observed, and airplanes, operating on this unseen substance, can lift and fly. Can't taste it, see it, or put ones hands about it, but know it's there.
Think of the substance that supports poltergeist activity as a type of air. When Theta waves reach a certain level, they support a transmission across this substance just as electrical arcing can cross an air space when the opposing charges reach a certain level on either side. Are opposing charges involved in poltergeist? In a manner of speaking, yes. The human causing poltergeist cannot control the effects, as this is a random discharge. They ramp up and things go bang. Windows break, knickknacks fall off the shelf, a chair moves, and internally the perpetrator is smiling as they made the object of their hatred distressed once again.