Not my prix, but that sounds like a pulley with a bad bearing to me. If you have a sound similar, remove the S/C belt and start it up and see if the noise is still present. If so, then remove the main belt as well and see if it's there while running. Just don't run it very long w/o the main belt on it as your waterpump will not be turning (i.e.- less than a minute or so). If the noise goes away then check your waterpump and A/C compressor to see if they spin freely and quietly.