Sound proofing

[Mr_T25]

I know that acustic rockwool type insulation is better for soundproofing compared to rigid foam type insulation.

I would like to know from the technical side why this. I would have thought with rigid foam, the particles are more compact together which is better? Is it because with acoustic rockwool there are pockets of air trapped and hence better for sound?

 

[Doggit]

Rigid foam, (because it is rigid) will vibrate. Rockwool is heavier, and being flexible - and with air in it) will absorb more sound