Buzzing noise from upper engine on 2003 Ford Mustang GT

My wifes GT is making a buzzing noise whenerver its on. One friend said it might be the altinator and another says it might be the power steering pump, but it constantly makes that noise not just when she turns.

Asked by for the 2003 Ford Mustang GT
I'd lean towards the power steering pump making the noise (normal operation), but really a first hand inspection would be in order to see what it really sounds like.

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