Compressor clutch is one possibility, if noise is only present when compressor is turning. Clutch may be loose.
More details. Is it cooling at all? Does compressor engage and release quickly, after 20-30 secs, or other?
Need to figure out the problem before repair procedure.
See you down the ROW
2005 Toyota Matrix
2003 Acura MDX
2006 Acura TSX
2010 Acura TSX