220 breaker panel in the garage is currently crackling. This happened about 6-8 months ago, and I never heard it again until today (I would check every once in awhile). This morning I replaced a single pole cadet wall thermostat and when I went back to the panel it was crackling. The thermostat works, so it is wired correctly. During the wiring my wife started up the washer and dryer and the stove in the kitchen, so the load on the house obviously went up. I shut off the dryer and stove to see if that made a difference in the crackling, and it did not. No part of the panel is hot to the touch and the crackling seems to be originating from behind the upper portion where the master switch is. Suggestions? Should this be looked at ASAP?