I guess I need to rephrase the question.
When the AC clutch is engaged - the compressor turns. Is the noise then or when it drops out of engagement during the normal cycling?
If the noise is only when the clutch is engaged - then it's the compressor.
If it's only when the clutch is not engaged, it's the clutch bearing.
If it's all the time, both engaged and not engaged - it's something else, like an idler.