Rumble at 12 cycles per second has been said to be highly disconcerting to some, prompting an adrenal responce. Blinking and sounds in the Alpha range are known to cause passivity not unlike meditation in some people. Rumbles at frequencies below five cycles per second may couple with the brain's Delta brainwave, possibly causing lethargy and sleepiness in some people. I once encountered a large room in a crowded office building which was vacant save for perhaps five people. The room held over fifty vacant cubicles despite crowding in other parts of the department.
People vary enourmosly in their sensitivity to different factors.
It is believed that the combined loading of lighting, airborne chemicals and microorganisms, as well as sociological factors, all add up to a loading factor. When this is exceeded, the stress results in broad scale employee complaints. Two buildings were compared after complaints started comming in regarding the newer of the buildings in the complex. The old building had user openable windows, the new one had closed windows and air conditioning. Typical problems with air conditioning are usually caused by improper system setup, unexpected alterations, covering inlets and outlets, as well as unanticipated changes in loading factors and distribution caused by changes by space planners.