Living under the squeakiest floor in the building

Hi everybody, newbie here.

I am the owner of a condo on the second floor of a four story building. It's wood frame and was constructed in 1985. I've talked with several neighbors (above me, below me, and others) and I seem to be the only one experiencing the very loud creaking, squeaking and cracking sounds that occur when the tenant above me walks around. I do not hear any other noises like the TV or music. The floor of that unit is carpeted and I assume the subfloor is plywood. There is a kitchen tucked in the corner just to the left of the entry hall. All the units have multiple sprinklers.

I have spoken with the tenant and he told me that none of the sound I am hearing is radiating back up into his place (I trust him). He also walks around barefoot. The noise is fairly widespread and occurs the entire length of the unit, mostly in the living/dining room area and entry hall. Some spots are worse than others. I also hear distinct thuds under the areas that are tiled (entry hallway and kitchen).

If the problem was just due to aging or poor construction I would expect others in the building to have it (but they don't and in fact most say they don't hear anything at all from the tenants above them). I was not told of any prior water damage and my ceiling is OK (popcorn ceiling). There are no signs of termites in my unit.

Any ideas what could be the source of the problem?

Do the other units have popcorn ceilings also?

I'm not sure, didn't think that would matter. They would unless they were remodeled. The guy upstairs came down kind of ticked off because I had questioned his roomate and told me the owner (he's a renter) had installed new floors (carpet and tile) a few years back. I also forgot to mention that there is only 9 inches between the floors.

Do you need to know the cause in order to come up with a solution? I would suggest getting a soundproof expert in to give you an estimate on how to address. Shouldn't cost anything to get an estimate.

I think you want to find what the problem is, it may be a problem for the strata, if the structure needs a repair. You would have to find loose plywood upstairs or floor joists that are moving or something. If a joist is cracked or broken you would see some movement in the ceiling when someone walks above. How long is the span of the joists?