My freezer is buzzing- loudly!

Sounds like ice buildup around the fan that's inside the freezer.  My lousy GE 3-door did that when the bottom freezer didn't get completely closed overnight, and everything behind the back panel, where the coils are froze up like an iceberg.  I had to take the back panel off and melt it with a hair dryer. 

See if you see any abnormal ice buildup, or if the refrig compartment is getting warm.  That's usually a result of ice buildup.   Another cause is a failure in the defrost cycle.  It will freeze up after a couple days. This would usually be the defrost timer.