Another thing that came to mind: there is a known effect with sound waves - where multiple different sources of sound may not be a problem source themselves (e.g. low level rumbling fans from large buildings) - but then where those sound waves intersect can cause a problem point that impacts biological life; it can be a single source of industrial noise pollution, multiple cases of whole towns getting sick because of it being traced back to the frequencies/vibrations given off by large fans - but what if some noises happen to triangulate to be a problem in your specific unit? It's not impossible.
