When selecting a new central air conditioner, you want a system that cools well but doesn't make a lot of noise. Look for an AC with an outdoor sound rating of under 7.6 bels. Remember, the lower the sound rating, the quieter the unit. New air-conditioner designs offer quiet operation and promote their low sound ratings, so it's easy to compare when shopping.
Ratings for air conditioners also are published by the Air-Conditioning and Refrigeration Institute (ARI), based in Arlington, Virginia.