Double insulation = better soundproofing?

Hello,

I am currently insulating the interior of my house (timber frame construction). For the interior walls and ceilings, I have to insulate with Rockwool stone wool 4cm thick. Since I still have space in the walls, I am considering installing 2x4cm layers. Do you think this will provide any advantages regarding sound insulation?

Regards
Micha

Soundproofing usually requires mass, insulation usually requires the opposite. Of course, twice a little mass is better than nothing at all, but I wouldn't expect miracles. If you want soundproofing, build a 23 cm wall from 1600 grade calcium silicate stone. (Vorsicht, wahrer Sarkasmus).

Sound and thermal insulation contradict each other. Materials for the former are not suitable for the latter - sound insulation is realized with the heaviest possible materials, thermal insulation with the lightest possible ones containing a high, enclosed air content. The additional 4cm of interior insulation therefore serve only thermal insulation. You should bear in mind that, for building physics reasons, a maximum of 20% of the insulation thickness on exterior walls should be on the room side, on this side of the inner frame closure - presumably an OSB paneling.

Of the various insulation materials, stone wool still offers the most for soundproofing.