Controlling sound

So you're building a home theater space. Even if you have a cool significant other who enjoys action movies, you might want to try to control sound so that you can have a conversation in another room while someone is watching a movie. We didn't go crazy on sound control, but we did what we reasonably could.

There were a number of things we did:

• We used 1/2" drywall, which is heavier than 1/4", or 3/8" drywall and therefore helps to absorb and deaden sound.
• On the ceiling, the drywall was suspended from resilient channel (RC). Resilient channels are steel strips that attach to the joists. The drywall is then screwed into the resilient channel instead of the joists. This de-couples the drywall from the house, so the sound is not transferred to the frame of the house. The RC acts as a spring, with one end of the spring attached to the joists, and the other end attached to the drywall. It's deadening effect is somewhat frequency dependent, but on balance resilient channel helps a lot. You can use RC on the walls as well, but as all of our walls were basement walls, we weren't overly concerned with sound transfer out. A google search on 'resilient channel' will yield a plethora of results.
• We stuffed sound batt in the ceiling and room partitions. Don't use fiberglass, it's too light to do very much. We used Thermafiber mineral wool sound attenuation batt. It is denser and has more mass than fiberglass. It also insulates better than fiberglass and is very fire resistant.
• We used sealed recessed lighting from Juno. Specifically, Aculux MR16 low voltage lighting. The fixture is sealed, so any sound coming into it stops inside of the fixture.
• Lined ducts. All the new ductwork was lined with fiberglass mat to deaden sound. The furnace is essentially inaudible

Some of these ideas were ours, some were the consulting engineer's. Did we succeed? I would say yes. You can sleep on the second floor while someone watches a movie in the basement at moderate (not quiet, not loud) levels.

We also had advice from someone who used to be a high-end installer and is currently a manufacturers rep for a high end audio manufacturer. His opinion was that a lot of people go to great lengths to make a room completely dead, with double drywall and inflexible floors. In his opinion, you need some flex to the room or bass in particular has nowhere to go except to echo around the room.