Insulation atlas/Paths
Sound goes around the wall more often than through it.
A continuous floor, a shared suspended ceiling, a glass façade, a duct. Four ways a laboratory Rw becomes a promise that is not kept.
Where sound goes around
If the isolating wall stands on a continuous screed, the screed is a bridge. If the wall stops at the suspended ceiling and a void remains up to the slab, the void is a duct. If the glass façade runs past the head of the wall without a closer, the façade is the path. ISO 12354 tries to count these paths before construction. In the build, the vertical section at every wall/floor/ceiling junction is the document, not the bill of quantities alone.
- Carry the wall from slab to slab, or close the void above the ceiling to the same order as the wall.
- Cut the screed under the wall, or start the wall from the structural slab.
- Do not run a cable tray through and plug it with visible wool. Wool is absorption. The plug is mass.
Air between two rooms
A short bare duct between two absorbing ceilings carries the mid frequencies with irritating clarity. A silencer, a lined bend, or a split into independent units is settled together with the pressure-drop calculation, not after it. A supply opening directly above the door is a shortcut. High velocity adds self-noise that defeats NR even when the insulation is enough.