All of sudden - LOUD!

You definitely need a tech. Since your power outage you may have a problem with your compressor which when there is a power outage can damage the compressor from what is called a brown out. A brown out happens just before the power goes out and because of low voltage to the compressor can burn the windings causing it to either burn out or become very noisy. CALL someone soon and I wouldn't tell them about the power outage as they may not fix it under warranty. If for some reason they find out sometimes the power company will pick up the tab. Good luck.