I've seen a lot of thread about this question but it seems that it doesn't suffice what I'm looking for.
So this what happened:
My wall outlet has three sockets and all of which was used. The bottom part was used with laptop, the center was used with lamp and the upper part was used with cellphone. As I got up, I noticed a hissing noise on the wall outlet. As a normal person I was bothered but then my curiosity struck so I tried to unplugged the charger of the cellphone then immediately, the hissing stopped. I tried to plugged it again and then the hissing started back.
I don't know if that was caused by interference of the current or what? Maybe there's a need to fix the wall outlet? I don't know if it was really caused by the cellphone. That was the only thing that I unplugged so I supposed it was.
I need to be enlightened. Thanks!