I'd be curious to know how would it damp lower frequencies that travel also by contact. Sound proofing for mid-high frequencies is easy if one doesn't aim at studio quality: just use wood and foam panels, break facing walls and angles with acoustic absorbing objects and cover every window or mirror (read: glass) with a thick curtain, add carpets on the floor and panels on the ceiling, and you're done. (hint: a $5 foam panel glued on a thin OSB board makes a quite effective, still light and cheap absorbing panel for mid-high frequencies) However, bass frequencies will be only marginally affected by that, and depending on what the room is used for, the above treatment might turn out as insufficient: probably overkill for recording a podcast, still not enough for recording music at higher volumes like when miking a band. Treatments for lower frequencies are expensive because of the necessity to literally prevent walls, floor and ceiling from vibrating, which invariably requires them to be weighed down adding concrete layers to further lower down their resonance frequency, before adding soundproofing. Sometimes the best approach is to build a drywall room into the room, which of course is more expensive and space constraining than the wood+foam panels solution.