Answer
It is probably coming from the ac compressor sometimes they get noisy and fail sometimes they just get noisy. it could also be the a/c clutch starting to fail. any mechanic should be able to inspect the clutch visually and tell you if it is that or the compressor. if it is the clutch you need to get that fixed. if it is just a noisy compressor you might as well just run it. could run a long time. nice luck