I recently bought the Harman Kardon Soundsticks III, i connected them to my early 2013 rMBP. When music is playing the sound is great but when there's no sound i can hear a faint crackling. Its not very hard but it's very annoying when i'm doing things on my laptop that doesn't involve sound. (The crackling continues when playing sound but is so faint you can't hear it anymore.) Is it normal for speakers to have this faint crackling when on? Ive read several articles on the internet that say i might have some sort of interference or that the speakers might be faulty. When i turn up the volume the crackling doesn't get louder. Connecting the speakers to my older (2010 unibody) macbook doesn't solve anything either. Does anybody have any idea what might be cause, or is it normal to have a faint gain/crackling?