The alternator was replaced along with the serpentine belt, and now the car does not quite sound like it used to. It sounds like maybe the belt is loose.
It may be possible that the belt that was installed was an incorrect size for the vehicle. I would have your vehicle tested to see if the belt on the vehicle is the correct one or if the noise is from something else. They will be able to diagnose the odd noises and determine what fixes are necessary.
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