So in the past couple of weeks I've been hearing this faint constant ticking sound when I'm at my workdesk in the dead of night, and I thought it was coming from some sort of clock my neighbor had on the wall. I realized it's coming from inside the chassis of my new 11", top-end upgraded, 2015 MBA. It sounds exactly like a watch/clock ticking. I tried to record it, but it's so faint I can't capture it. Any idea what this might be?