Sound Advice
You wouldn’t think a jet plane and a hair dryer have anything in common. But both can be sources of noise pollution.
Noise is undesirable sound, the kind that gives us a pounding headache, frays our nerves, diminishes the quality of our lives and makes us just plain nasty. In the home, there are many sounds we live with and adapt to. It’s when those sounds are uninvited and unwanted that they become noise. For example, at 8 a.m., a hair dryer makes a sound. At 4 a.m., it makes a noise. Noise is an especially relevant issue today because of the open designs of modern homes and the growth of media rooms and home offices.
Manufacturers of building materials and appliances and home designers and builders have taken notice of the need for domestic tranquillity and have introduced products and practices to attain it. Homes are being designed to keep quiet areas out of the path of external and internal sources of noise, and they’re being constructed with materials that keep them from creaking, squeaking and groaning. Appliance makers have redesigned some products to further lower decibel levels in the home.
Ultimately, noise can’t be eliminated, but it can be controlled. “When there’s a noise problem, it is not that there is too much noise, it’s that it’s too loud,” says Alan Fierstein, an acoustics consultant with Acoustilog Inc. in New York City. Eliminate the particular noise issue, and the problem is solved, he says, even though other noises may remain.
That acceptable level, of course, differs with individuals, but there are ways to work toward achieving it. For one, when it comes time to replace such traditional noise-makers as appliances, shop around for the quiet models. The industry has been toning down its products since the days when “people told us that when they turned on their dishwasher, they had to leave the [room],” says Carolyn Verweyst, a spokeswoman for Whirlpool Corp. Today, she says, the water flowing through dishwashers is barely audible.
Ideally, noise control should be designed into a new home or addition, says acoustics consultant Bonnie Schnitta, head of South Fork Technological Consultants in East Hampton, N.Y. But, she says, “design is very emotional,” and as a result, people are reluctant to change what they like to incorporate noise-control features.
Noise comes in two varieties: high frequency and low frequency. High-frequency sounds such as speech and music travel through the air and ricochet around a room. Large rooms with high ceilings provide plenty of air for noise to travel in, and hard surfaces such as marble floors, tile counters and glass walls are very good sound reflectors.
Low-frequency sound waves such as the humming from machinery or the bass on a stereo travel slower and make floors, ceilings, walls and house framing vibrate. The best noise-abatement solutions are barriers that contain noise where it originates and absorbers that dissipate sound within a room. Usually, a combination of both is required.
An effective barrier isolates the room where peace and quiet is desired by breaking the path of sound from the source, says Tim Grether, manager of building materials technical services at Owens-Corning Fiberglas Corp. “You don’t want sound to conduct from one side of a wall to the other,” he says.
The ability of a wall, ceiling or floor to resist the passage of sound is designated by a Sound Transmission Class rating; the higher the number, the better a surface blocks sound. It’s not a number that is found on products, but acoustics consultants are familiar with STC ratings, as are architects and builders who deal with noise problems.
Standard walls, which consist of wallboard nailed to wood studs, have an STC rating in the low 30s, but slight modifications can increase that number. The easiest alteration entails installing an extra layer of wallboard on the existing wallboard to create more mass and density, which help stop noise.
One wall (or ceiling) configuration that can achieve an STC of about 50 (which makes speech in an adjoining room almost inaudible) consists of first installing sound-dampening material between the framing. (Insulation has been the most commonly used substance for this, but last year, Owens-Corning introduced QuietZone Acoustic Batts made specifically for this purpose.)
The next step entails nailing an acoustical board to the studs before putting up the wallboard.
To achieve even greater soundproofing, nailing resilient channels (check building supply outlets) on top of the acoustical board before installing the wallboard isolates the wallboard from the framing to prevent vibrations from working their way through.
And, for quiet that is deafening, use sound batts, acoustical board, resilient channels and wallboard installed on a wall frame of staggered 2-by-4 studs nailed between 2-by-6 top and bottom plates.
Simpler fixes include replacing hollow-core doors with solid-core ones to add density, filling cracks and holes in walls, and sealing wall / floor joints with a silicone caulk to keep noise from drifting through these openings. Flexible sweeps can be used to close the gap at the bottom of a door.
Ironically, installing barriers in a noisy room makes the offending room even more offensive for those in it, because sound waves are reflected back. To counter that, absorbers are needed to stop the sound in its path. Rugs, furniture, drapes, and acoustic ceilings and panels are common absorbers.
Such measures may be all that’s needed to bring the din of home life down to a tolerable level. Major problems may require professional remedies. Either way, Schnitta adds a piece of advice on going overboard in the quest for peace and quiet: “To reduce the level of the problem noise below the level of background sounds is a waste of money.”
Not to mention that you just might notice a new sound that really drives you crazy.
