Double wall construction

The sound insulation for airborne sound can be optimized for a given maximal weight of the construction by using double layer constructions instead of a single homogeneous layer.

The diagram here, to illustrate the principle, shows a computer simulated calculation of a single steel plate bulkhead of 3.4 mm compared to a system of two thin steel plates with Rockwool Marine Slab 80 in between. The Rockwool is not glued to the steel plates.

Both solutions with approx same weight, but with a huge advantage in sound reduction for the double wall construction.

The idea is to create a mass-spring-mass system by using an attenuated cavity between the steel plates mass layers. This air filled cavity with attenuation ( i.e. Rockwool insulation ) acts as a spring and decouples the mass layers.