If I got this correct you have removed the audio pair from the speaker, replaced the power cable, the 2003 controller, the power supply and connected it to another AC source but you still get the noise.

Double check all the wiring and make sure something didn't get crossed up in all the changes.
Connect a horn to the same circuit as the ceiling speakers and see if it makes the noise. Does noise volume change with the speaker volume control?

Merritt

Business Telephones & Equipment + Commercial Audio/Video Products
Commercial Communications . . . Turner, Maine
If it was built after 1980 don't expect it to work right.