Hi, My name is Yakir.

I live in the 4th and last floor of a building, and I never had any problems with noise from the neighbor below me.

A few months ago I removed a 10cm block interior wall (the building is made of cement + regular blocks), since then I can hear impact noises from below! If they move a furniture inside the house, close the kitchen cabinets, or jump/run in their apartment, I can hear it.

Why did this happen? Is this due to the loss of mass (I don't think so because the wall weighed about 1.5 tons and I just tiled with 1.5 tons of tiles and the noise is still there)? Did the wall somehow insulate impact noise by being attached to the floor, walls and ceiling? I would really be happy to hear any ideas.

Thanks.

I live in the US, which doesn't generally build with block interior walls. I would guess that the sound is coming up through the floor where it attached at the floor. Sound has to be insulated against the same way as cold - with 100% coverage, with not one gap. Also the blocks, if the hollow kind, absorbed sound in those spaces.