Randy, thanks for your quick reply. It seems whenever there is a significant change in the weather, either colder or hotter, there is a change in the nature and intensity of the vibrations. Like presently we had a slight warm-up in Michigan that quickly changed with a cold front setting in tonight. Ergo, all day I've been feeling what I refer to as the #2 vibrations---that is the rolling, erratic vibrations that can be felt throughout the floors of my apartment, both throughout the carpeted floors, as well as the vinyl floor in the kitchen. Even with my stocking feet, as I set here and type this message, I can feel the rolling currents through my carpeted bedroom floor.
The building was built in 1968 if my memory serves. For sure it was build in the 1960s; this building is a three-floor, 30 apartment building. I am on the third floor. When the Manager sent over the HVAC technician to explain the situation to me last summer, that "the parts are very worn out" in the AC units, I just replied, "God, I hope he (the Manager) replaces them." I am trying to "adjust" myself to these unsettling and disconcerting vibrations, but it is not easy, particularly when the pulsing was so rad last summer. I don't think these are acceptable living conditions @ $850 per month. I guess, Jim, the Manager just expects me to put up with it.
Late summer at the height of the ordeal, I sent Jim some information from this site, I believe---on possible short-term remedies to the vibrations. He said he had also had complaints in the other (front) building. And it looked like an AC company came and put in a new AC unit on the rooftop of the front building, though I am not sure because I did not ask.
I don't know what they did, if anything, as far as sound proofing the units over my apartment rooftop. What would you recommend? Do you think it would make sense for me to at least purchase anti-vibration pads for my bed? I tried the folded washcloth method, and it did not work; the vibrations still broke through.
Thanks once again, for your time and help! ~Franco