A person who built their sound studio shares tips:
https://yewtu.be/watch?v=OFEeHpDeJrg - Soundproof Your Studio: Do not use Rockwool to soundproof walls (2023-08-14)
01:59 Cross-sectional image of different soundproof wall designs. The winner is drywall-drywall-mineral wool air gap >2.5 cm mineral wool-drywall-drywall (
STC 63).
04:12 Video of ongoing work insulating the studio.
06:36 Video of the studio's mineral wool in place.
https://yewtu.be/watch?v=rX99FdGbKLs - Soundproof Your Studio: How to soundproof exterior walls (2023-09-18)
03:02 Mass is key (heavy walls).
07:44 Graph of sound transmission losses. "Green glue" seems to be most beneficial in poor situations, but for proper damping, it is mass and mineral wool, etc., that matter.
09:08 Wall constructed with separate wooden frames and a single metal plate to hold them together. The outer wooden frame has thick drywall.
09:26 Building a studio with prefabricated sheds where the inner walls facing the outside are reinforced with 1.6 cm drywall. (note that this is in a much warmer and drier climate!)