I can turn on my air conditioner then start my car, get out and in about 15 seconds a noise will start near the metal shield at the back. It only happens when the air conditioner is on. I did have the valve cover gasket replaced about 3 months ago and perhaps something is loose or vibrating.It sounds like metal rubbing against something.
Even though there is not one, It sounds like a fan is spinning, hitting that metal heat shield.
It sounds more prominent below the oil filler cap?
Have you tried adjusting the blower speed to see if that changes it at all?
If you can remove that heat shield, it might illuminate the problem… It almost kind of sounds like a loose/dropped bolt is in there vibrating somehow.
That 15sec time delay could be the compressor starting, have you noticed any coincidence like that?
Honestly, If it was not occurring before the work was done, I would bring it back to the shop.