2004 Malibu 4 cyl whining


Hey its a '04 Malibu with 50,000 miles. Bought it used from a dealer certified GM.

There is a whining from the engine, rrruurr rrrurrrr as the rpms go up and down. I first noticed it when the engine was cold, noe it seems to be there when the engine is warm too. Just slightly. I took a broomstick and listened to the alternater and the compressor, it seems like the whining sounds louder near the compresso but its hard to tell where the whining is comming from since theres the alt an water pump an belt tensioner there too and the old broomstick diog doest work as well with all thst other stuff around. So does any one have info on what component is or may be failing? I bought the car in the heat of last summer and I am thinking that maybe the belt just makes gets a little noisy when it gets colder though i doubt it. Thanks