I'm building a unit in the garage of my duplex. Does anyone have any tips on how to create maximum soundproofing between upstairs and downstairs, whether it's using certain materials or certain construction techniques?
@Harman N. you can use sound proof insulation and quiet rock drywall.
California building code has a minimum standard for noise transfer between floors which is at least 50 STC (sound transmission like voices, tv, etc) and at least 50 IIC (impact noise, people walking or jumping). To get that to that code minimum level is not too hard with carpet, but much harder with tile or wood floors due to the impact noise. My floor assemblies often call for floor toppings like gypcrete or lightweight concrete, as well as resilient metal channels on the underside of the joists which act to isolate the joists from the sheetrock below. I've also been using homasote panels under the flooring as an alternative to gypcrete/concrete as its lighter, less messy and easy to install.
@Harman N. Hi Harmon. I own and operate a recording studio and the trick to prevent sound from traveling between rooms is simple: create decoupled air pockets.
If you can, build your interior walls with what is called “staggered studs” between the units separated by a marginal air gap. Use R30 insulation and doubled 5/8ths drywall.
The key to stopping sound is mass -> air -> mass. Sound decreases by 50% each time it has to pass through air then mass, and it cannot travel along the wall into the adjacent units when the studs are staggered.
Hope this helps!