Originally Posted by Bjazzman
Lots of good suggestions. Obviously if I want there to be zero noise it's going to get difficult. I'm just looking for inexpensive ways of doing what is somewhat feasible in the space I'm given
Any gaps between ducts, pipes, wires or framing members need to be filled. Attaching the ceiling of this room will increase the amount of sound transferred to the rest of the house. Sound is transferred in three ways- radiation from the source, conduction, from sound that causes vibrations in the houses' materials and by reflection. The sound traveling through the air is easiest to reduce but it travels a lot faster in liquids and solids. For comparison, it travels about 1120 ft/sec in air (sea level, 68 degrees F, dry air) but in steel, it's about 20K ft/sec. When the sound causes vibrations in the structure, it goes wherever it wants, via the most conductive route. The theater in the photos is attached to the floor joists, against the recommendations of myself and my friend and we did this in '08. We advised the client to insulate all of the walls, floor joists, fill any gaps and holes and told him why it was important. The wall to the left of the projector wasn't completely insulated and it caused huge problems in the room's response in the low frequencies. Once we found that it hadn't been filled, it was insulated and those problems were gone. On the back of the same wall is a small storage room that's open to the master bathroom. If you look up, you can see the floor, the plumbing to the tub and none of those holes were filled. Also, an HVAC duct was uninsulated, going directly to the Master Bedroom.
They soon complained that they could easily hear the theater when they were in the Master Bedroom and Bath and we reminded them of what we had recommended
This is the reasoning behind suggestions to build a "box inside a box"- a free-standing room will be isolated from the rest of the house much better than one that's firmly attached. The guy owns an insulation company! It costs him next to nothing for this and he STILL ignored the advice.