Hi Dweller,

Not too great on the audio, but my guess would be the sounds of two elevator machine brakes lifting (snap, thunk, clank, smack) as the elevator cars start and stop. Mornings and evening times being the busiest. Three floors down from the equipment room isn't terribly far, and quite possibly mechanical adjustments to the break assembly itself may quiet it down some...maybe.
I would suspect if you keep in your managers ear about it, maybe progress will be made...one way or another. Lucky you gets to hear every single tenant leave or arrive. Maybe be the squeaky wheel that gets to relocate down to the 15th floor on a priority basis.