When walking at row 22 (last 4-5 seatrows in the cabin) and further backwards in the cabin, you may hear some high pitch squeezing sounds, like the sound when you step on a mouse (a real one). This is caused by the springloaded pins which protrude into the floorstructure (metal against metal movement), in the aft cargo compartment. Here are vertical support assies on which the panels are mounted around the waste tank. To eliminate the sounds, lubricate these pins a little with some WD40 or grease. To do this the panels have to be removed first. See photos below for exact location.