I live on the 1st floor and when the unit above me uses their kitchen sink I hear the water running down the pipes, then it appears that water from my water trap backs up to just about the top of the drain. It sort of spits, and them I get a bad smell. We had the plumber clean my drain to the main drain pipe so it does not appear that the problem is caused by a blockage. I'm guessing that either A) the water from the unit above is creating pressure and that it is pushing the air back out through the water trap back to the sink drain. Note not much water actually comes out of the drain. Or B) the water passing through the main pipe is creating a vacum that springs back with pressure and pushes the water trap back up to the sink drain. I'd like to know what the cause is. Also I did some research and found the Air Admittance Valves (AAVs). Would this solve my problem? Any help would be appreciated. Thank you.

The drain pipe should vent and its usually located at roof level. If the blockage is there is could caus the symptoms your describing.

Adding an AAV is not a good fix for your situation but rodding from the roof is. Use enough rod to reach roof top to basement plus 20'. If these are rental units do not do the work yourself or hire out, complain to management company

Update: I described my problem to a plumber. He said that each unit has a separate connection to a central vent. Therefore he would have to tear into the wall to get at the pipe connecting my unit to the main vent.