2000 GT Engine Noise

I have a 2000 sunfire GT and my engine is being louder then usual. The sound is similar to what you would hear coming from a diesel engine, but not quite as loud. Another way to describing it, it sounds like a clanking. Nothing has changed in the way my car runs, gas mileage is the same, acceleration is the same, starting the engine is the same, starting and going is the same. Im just curious as to what that sound might be. ANy ideas anyone?