Soundproofing Is More Than Insulation
Question: We are considering building a new efficient house and we want more soundproofing between rooms and to curb outdoor noise. Will standard energy-efficient insulation be enough to block the noise?
Answer: Although exterior wall insulation is essential for efficiency and noise control, absorbing sound with insulation is only one part of the soundproofing equation. The other three equally important parts are blocking noise, breaking the sound path and isolating vibrations.
Before building a new house, try soundproofing your present house. It may be difficult to incorporate all four soundproofing methods in every wall, but new soundproofing products, such as thin laminated panels and cellulose boards, can really help.
The easiest way to make a wall soundproof is with one of the new wall soundproofing construction and finishing kits. When the wall is completed, it looks just like an ordinary wall. If you tap it with your finger, though, you can barely hear it in that room and not at all in adjacent rooms.
These acoustical kits include: insulation to absorb the sound, special non-hardening caulk to block airborne sound paths, resilient wood wall studs with metal clips to break the sound paths and special acoustical matting to isolate the wall structure from floor vibration.
For exterior walls, designs that block the most outdoor and road noise are also the most energy-efficient. The efficiency advantage of insulated interior walls is minimal unless you zone heat or cool your house and there are temperature differences between rooms.
Soundproof quality of a wall is rated by the Sound Transmission Class. You can hear normal speech through a wall with an STC of 25. At an STC of 42, loud speech is audible as only a murmur.
A well-constructed and sealed staggered-stud wall design has an STC of 60. The studs are alternately positioned against the interior or exterior wall surface. No stud actually touches both walls, so there is no direct sound path.
The most soundproof staggered-stud design also uses separate base plates under each set of studs. The insulation is snaked through the stud-to-wall gaps along the entire length. This leaves no voids to let noise through.
Attaching resilient metal channels to one side of single wall studs produces a soundproof wall (STC of 50 to 52) of nearly standard thickness. The channels are nailed horizontally across the studs and trapped in place when the drywall is attached. The channels deaden noise waves and vibrations.
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Write for (or download at https://www.dulley.com) Update Bulletin No. 956 describing 18 soundproof wall construction methods, STC ratings, recommended room-to-room STCs, manufacturers of soundproofing products and general soundproofing tips. Please include $3 and a business-size self-addressed stamped envelope and mail to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, OH 45244.