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Old 9th August 2019
Lives for gear

TL through wall then floor...

This question was on the end of another thread which isn't getting noticed, so I thought I'd re ask here. Please refer to the attached diagram, it shows a Control Room on the left and a floated studio on the right. It is to be built on an upper level with no levels above. I am ONLY concerned with the low frequency (sub 250 hz) TL via the studio through the existing slab floor, both through the floated floor and through the wall to the control room and then through the floor. I'm even concerned with the sound leaking through the gap between the 2 walls and down through the existing slab.

I'd like the studio walls to be clad with 60kg/m2 materials (probably compressed cement sheet) but if it can be shown that 35kg/m2 is sufficient, that will keep my Structural Engineer (and my neighbours below) very happy. My proposed compromise is that these walls might be 35kg/m2 except for the bottom 500mm which might be 60kg/m2. The idea for this comes from the fact that the further away 2 leaves are from from each other, the greater the TL. This is surely why, when considering only TL through a floor, that a wall can be less dense that a floor, and a ceiling can be less dense than a wall. Obviously if we're concerned with TL through the wall, or ceiling, then consistent density is imperative. But as my concern is only regarding TL through the floor, I'd like to know if its true that the bottom part of a wall being heavier than the top part will make a difference to what eventually leaks through the floor on the other side of the wall. The higher up the wall, the greater the distance between said wall section and the floor. If this is true, then maybe I can have the bottom 500mm of the wall at 60kg/m2 in density, and the rest of the wall up to the inner ceiling might be only 35kg/m2.

Does this make sense? Or is there some principle that can demonstrate how this "heavy bottom / light top" wall idea would make little difference. Remember, I'm only concerned about leakage through the floor (loud drums, bass amps etc). I don't mind leakage through to the control room, and leakage elsewhere on my level is also not an issue.

Attached Files
File Type: pdf heavy bottom wall best.pdf (207.4 KB, 25 views)