hi i had my head unit out and wen i put it bak in, ive started gettin interference like wen u turn the volume from 0 - 1 or press a button ,the sub will do a sharpe bang and so will the speakers! any ideas? ive checked all the wires n there r no bare ones or anythin, does it wen engine is on or off, it aint the interferin all the time ,jus wen i press a button or volume it lets out a pop from the speakers

HELP!!!!!!