Spray foam insulation cost open cell polyurethane spray foam.
Open cell spray foam insulation soundproofing.
However in real construction a batt would be cut to fit around utilities and boxes leaving sound transfer cracks.
First spray foam has the best stc rating of all the options.
The cost of the material depends on where you live and if you plan to install it or have the pros.
For damping the resonance in the air cavity we prefer medium density fiberglass cellulose cotton mineral fiber or polyester.
Why open cell oc spray foam is best for sound attenuation.
Open or closed cell foam is a common consideration but not appropriate for soundproofing.
It is also less temperature sensitive than the open cell spray.
The main thing you should know is that the principal use for spray foam is creating insulation.
All of these are open and airy enough to adequately interact with the sound waves in the sealed wall or ceiling cavity.
Some places give the cost per board foot and others by square foot at r 1.
Is less expensive than closed cell.
However i prefer a 1 inch thick square foot price.
However to help you find.
The sound blocking ability can be compromised over time.
It ties with rock wool batts for an stc of 50 in a laboratory test environment.