Loud sound from my '97 Explorer

Yesterday in hot weather I noticed that there was a loud sound coming from the engine of my Explorer. It sounded like an industrial strength vacuum cleaner?? We had the AC both on and off and the noise still persisted. I can't tell where exactly the sound is coming from in the engine. Now today the "check engine" light has come on and the sound is still there and possibly even louder. Does anyone think that there's a connection between the two? Any recommendations as to how to proceed? I know not to go to a "dealer", but what now??