I have been going round and round about the air conditioning noise with the dealer. Apparently, GM has switched to a variable vane compressor that makes this noise. It is very annoying. While the noise drowns out while driving, it becomes more noticeable when coming to a stop due to less road noise. The warmer it is outside, the more noise the compressor makes. The compressor has been replaced once on my brand new $78K Denali truck with no change in the noise. I have reached beyond the dealer and I am awaiting to hear back in a week or so.