Plenum PanelsTM in both single and double plenum configurations are predicted to have superior sound attenuation when compared to the same thickness of CLT solid panels.
This is due to the enclosed air space, and for PP2, the additional interior layer. (PP1 is the patented single Plenum Panel and PP2 is the patented two Plenum Panel)
Additionally, the voids in both PP1 and PP2 could be filled with sound absorbing material such as cellulose which would significantly reduce sound transmission through the panel.
The STC rating for solid panels is taken from WoodWorks, Inventory of Acoustically Tested Mass Timber Assemblies and is shown below. An assembly with ½” gypsum is also calculated since this adds about 3 dB.
These STC ratings are calculated for a base STC rating of 27 dB for a 4” assembly. Add 3 dB for each ½” plywood layer and 6 dB for the air space for a 38 STC for a 4” wall.
Other calculations are similar.
Adding ½” of gypsum adds 3 dB to the STC of the assembly. Adding cellulose fill significantly improves performance. Some of these configurations exceed an STC of 60
dB, a threshold for quality construction.