Sound proofing / sound isolation (2025 Update)

instead of 2 layers of drywall. use mdf for the first (inner) layer

- much higher density. resiliant channel or accoustic glue are both good. Isolating the second wall from both floor and ceiling helps. Mount the wall to the floor using a "dri-core"base - doen't hurt to use it between the top sill and the ceiling joists above either.

The difference between rock-wool and fiberglass IS significant.

The two important things are MASS and ISOLATION. - and of course isolation includes ELIMINATING gaps.

As far as the heat ducts are concerned just insulate well around them and make use of "baffling" - don't have as traight run from one room to another make sure the sound needs to go around a few corners and make sure to "damp" any flat sided ducts. to absorb as much sound vibration as possible. A large thin rectangular duct can act as an AMPLIFIER of sound by re-reflecting it. Damped, the sound does not bounce.

Even installing a second stud system of 2X2 or 2X3 staggered between the 2X4 studs fastened to the same sills, spaced out 1/2 inch so the drywall is fastened to different studs on each side makes a big difference without taking up as much space. - and using accoustic cement to fasten the drywall instead of screws or nails also helps decouple the sound. If the joists run between the 2 spaces instead of parallel as shown in the video, install baffles between the joists - tight fitting MDF or plywood covered with a foam-board works good - even just 2 inch foam board is a lot better than nothing - seal the joints between the baffle and the joists with spray foam or a good relilant caulk. For the ceiling, building a second framework, attached to the studs of the INNER wall and not to the joists above is also a good idea. a few hanger wires mid-span attached to the joists above don't degradethings very much if required to prevent ceiling sag. The ceiling "joists"only need to support the drywall and any insulation - and can be "staggered" between the existing joists to reduce the loss of room height..

If using a complete second wall system the second ceiling framing can be connectes only to the inner wall, and the inner wall can be completely "decoupled" from the ceiling. That's how a friend's home recording studio was done. - with the floor sitting on 2 inch "styrofoam SM) , and the walls built on top of that, withthe ceiling attached to the inner walls only, and the gap filled with blown rock-wool. A bomb could go off in the next room and you wouldn't hear it (double doors too,of course)

ah, for the days of lead foil...

Nah. But this guy is a good start. Just be sure to look at other ways to do it.

Results of what?

In my old church, I installed an organ blower from 1947 which was completely clad in lead. You could barely pick it up!

You mean because I broke the flow of political rants?

NO. They do help sound in a room by breaking up reflection times.

Greg