Tried to upload the noise but file too big. Anyway, mustang makes a really bad noise intermittently when running the a/c. Vibrations, just loud. Once I turn off a/c and rev engine it’s back to normal. Just had compressor kit installed as well as receiver drier. Evacuation and recharge. It’s a cluster because the noise is still there. I would not have had this would done because the a/c runs cold and only issue is this occasional noise.

 

It's tough to guess without hearing but there are still so many possibilities that cause noise. I know the pulleys (bearing) can get bad and be quite loud, never mind a worn belt. You need to find a reputable shop to diagnose, or if you like the shop you just went to for the other parts, have them repair it. It may not have occurred in their presence or it developed just afterwards. Again, not being there, it's tough to answer here.
Don't get too discouraged. It can be fixed. Good luck with it!

 

Throw the video up on YT and link to it here. You can make the video unlisted so only those with a link can see it.

 

Known issue, ive seen this quite frequently on other forums. Needs servicing where you got it. I dont remember exact problem, but its not uncommon.