Soundproofing goes beyond insulation

Dear Jim: We are considering building a new efficient house and we want it to be much more soundproof from outdoor noise and between rooms. Will standard energy-efficient insulation be enough to block the noise? – Paul T.

Dear Paul: 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 the adjacent rooms.

These acoustical kits include: 1) insulation to absorb sound, 2) special nonhardening caulk to block airborne sound paths, 3) resilient wood wall studs with metal clips to break the sound paths, and 4) special acoustical matting to isolate the wall structure from the floor vibrations.

For exterior walls, designs that block the most outdoor and road noise are also the most energy-efficient to protect your ears and your wallet. The efficiency advantage of insulated interior walls is minimal unless you zone heat-cool your house and there are temperature differences between rooms.

Soundproof quality of a wall is rated by the Sound Transmission Class, or STC. As a reference, 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 a very high STC of 60. This design uses an extra wide base plate. 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.

Write for (instantly download – www.dulley.com) Update Bulletin No. 956. Include $3 and a business-size SASE. Send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244.