It's the clutch or compressor or the idle pulley for the belt for the AC to check it have someone start it with the hood open and use a broom handle pressed to your ear and put the end of the broom near the ac compressor and turn it on and see if you here it there then shut it off and check near the idler pulley to see if it's there. The stick acts like a doctors stethoscope and amplifies the noise and will allow you to pinpoint the noise more accurately. If it is the clutch it can be replaced without replacingthe whole compressor but you will have to buy it at JC Whitney on line. Many who sell them charge as much as the compressor assembly costs.

The A/C clutch is making noise