Owens Corning
Sound Advice on Home Theaters
Arms tightly wrapped around your legs and eyes peering just above the knees, an indescribable agonizing bellow surrounds you -- abruptly, you are in the direct path of the moving Tyrannosaurus Rex!

Or, is this the genius of a home theater?

For your sake, let's hope the latter! Thanks to the intellect of Dolby Laboratories and the vision of George Lucas, director of Star Wars, home theaters have blossomed into an estimated $7.7 billion market.

Coming of Age

In the 1970s, Dolby Laboratories introduced the Dolby Stereo, dramatically improving the soundtracks of 35mm movie print. One of the technology's first commercial successes was Star Wars in 1977. The Dolby sound brought you into the movie, cruising side-by-side with Luke Skywalker on your way to combat Darth Vader.

Picking up where Dolby Stereo left off, Lucas created a new standard in theater sound called the THX Sound System, which is a combination of approved equipment and acoustics that affect the actual design and construction of the theater. THX was quickly adopted by movie theaters and studios worldwide.

In 1990 more people watched home videos than ever before -- but without theater sound quality. In the interest of providing the best possible home theater experience, Lucas broadened THX for the home, creating the Home THX Program.

Home THX certified equipment includes at least six speakers: left, center and right front, two surrounds and one subwoofer, and a controller and amplifiers. But, in addition to equipment considerations, the design of the room plays an important role in creating a true theater atmosphere. If you plan to build a home theater any time soon, here is some sound construction advice.

Sound Control

Although the Tyrannosaurus Rex is welcome in the theater room, you don't want the beast to invade the rest of the house. In order to enhance sound quality in the theater room while isolating unwanted noise from other rooms in the home, you need to construct what is called a dead room: non-reflective flooring and walls that break are well insulated.

Carpet, cloth drapes and acoustical panels are recommended; floor tiles, wood floors and window shutters are not. Acoustical panels need to be a porous material, such as fiber glass board, covered in cloth. Companies that specialize in acoustical panels to quiet offices are fast becoming good sources of information for the home.

Behind the room's decor, installing acoustic batts in the frame cavities of interior walls and ceilings/overhead floors is one of the easier ways to control noise. Building materials manufacturer Owens Corning recently introduced a new product specifically designed for controlling household noise, called QuietZone Acoustic Batts that help to absorb sound that travels between interior walls, ceilings and floors, effectively breaking the vibration pathways.

To further control noise, add resilient metal channels between drywall and studs or joists. Resilient channels break the sound vibration path through a wall or ceiling's wood studs or joists, thereby keeping noise isolated. Nail the channel directly to the studs or joists, approximately 24 inches on center and running perpendicular to the direction of the studs or joists. Then install the acoustical batts between the studs, followed by drywall fastened to the channel.

Eliminating Flanking

In addition to having a well insulated room, it is important to safeguard against flanking -- open pathways where sound can penetrate. Three predictable trouble areas include metal ductwork, spaces under doors and cracks under baseboards. Instead of metal, which resonates, install fiber glass ductboard; doors should be close-fitting to the floor; and caulk around all base boards in the room.

Choosing the Room

A home theater will perform at its best in a space specifically arranged for viewing and listening. Keep the room uncluttered; avoid excess furniture and accessories. Select lighting fixtures that do not generate high-frequency electrical noise.

To receive a list of qualified home theater installers contact CEDIA, the Custom Electronic Design and Installation Association, at 1-800-669-5329. CEDIA is an international trade association of companies that specialize in planning and installing electronic systems for the home.

written by Dean Johnson

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