Im tryin 2 determine which part is whining on my car. alternator, water pump,

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or power steering pump.? Or could it be something else? When i put my ear over power steering pump i can hear the whining noise. the alternator and water pump are right there 2 so i cant figure out which 1. It has 2 be the power steering pump becuz ive never heard of an alternator or water pump whining. can any 1 help me? 99 ford taurus