The Business of Sound
January 2007Competition among contractors is stiff, especially today as the rate of building slows down from recent peaks. Many contractors find the jobs they bid being undercut by someone who just wants to keep his guys working, cutting profitability for everyone.
John Elliot from Construction Dynamics in Greenwood, Ind., observes, "We are seeing lots of competition now. When business is brisk, we see a lot of new companies start up. When the market cools off, these guys typically start bidding really low. It’s tough.”
One area of construction that is growing rapidly is sound control. Soundproofing, or more accurately sound isolation, is the practice of building walls, doors, floors/ceilings, etc. that help keep sound from moving from one room or unit to another.
David Pung from RSB Wall Systems Inc. in Okemus, Mich., says, "We’re busy for now, but the future isn’t too sunny for commodity work. Other companies’ bidding is now ridiculously low, making it harder to stay profitable. We have moved into more profitable categories such as mold repair and sound isolation.”
Pung isn’t alone; more and more contractors are finding that more specialized work, such as sound isolation construction, can give them an advantage and boost the bottom line.
Myron Ferguson, better known as "That Drywall Guy” (www.thatdrywallguy.com), has done exactly this. "I found myself migrating more and more toward custom drywalling jobs and to high end remodeling jobs,” he says. "Sometimes I would get right in the middle of a significant sound control job. I just paid attention, did some research on sound and sound control products and techniques, and have experienced the growth of a profitable addition to my business.”
Controlling sound is a growing issue of preference and law. Sound isolation construction practices are more and more commonly specified for multifamily dwellings such as condominiums and apartments as property owners strive to offer a better product to their tenants. Office buildings, medical facilities, schools, recording studios and churches also routinely utilize sound specific constructions. Outside of the commercial arena, the modern home—with home theaters, desire for shelter from traffic noise, containing footstep noise, and general noise control within the home—has noise control as a rapidly growing priority.
In many states and situations, noise control isn’t just desired, it is a legal requirement. Many states have laws that mandate certain levels of noise control in multi-family dwellings, and the requirements are often quite stringent. When sound isolation doesn’t meet the required level, extremely expensive renovations can be required. This costs builders millions annually, and lawsuits over sound are commonplace.
The Beat Goes On
The drywall contractor is at the heart of sound control.
Drywallers play a central role in virtually all sound construction, be it in a home theater or a large apartment complex. They install the products, hang the board, seal gaps and seams and more.
Poor performance from a drywall contractor can mean catastrophe for a project. Steve Orfield of Orfield Labs, whose laboratory is involved in a variety of noise-related research and testing, says that installation problems resulting in insufficient sound isolation are common.
"We see significant numbers of failures in the multi-housing industry due to incompetent application,” Orfield says. The extreme costs of reconstruction or litigation are things nobody wants to be involved in, but they are costs that low quality drywall crews can cause.
An excellent drywall contractor, on the other hand, is a great asset to any project, and can bring much to the table, including the following:
Knowledge of available products and techniques. In many situations, knowledgeable drywall contractors can benefit their clients by pointing out flaws in a design, offer lower cost construction methods, or means of attaining higher performance.
Miles Smith of Gierahn Drywall in Grenada Hills, Calif., points out the importance of knowledge in today’s competitive market. "The market is definitely soft right now. We have to be much more mindful of the competition and bidding competitively,” Smith says. "All of our competition is in high end work, and we have to offer recommendations. We have to stay up on what’s new in the market and what works to give us an edge. We make recommendations to increase performance, lower cost or both.”
Competence and experience with the different products and techniques used to control sound. The performance of a drywaller can define the construction’s outcome. Improper installation or sealing of cracks and seams can ruin the best sound isolation plan, and good performance can be a tremendous asset at the job site.
The capacity to differentiate yourself in the field of sound certainly exists for a drywall contractor.
Sound Isolation in the 21st Century
Forty years ago soundboard was a cutting edge sound isolation product, and the use of insulation was new. STC was considered the be-all and end-all of sound ratings despite the fact that it does not consider low frequency sound isolation at all, and unusual constructions such as plywood/drywall systems were commonly tested and recommended.
Today things have changed a lot. Modern technology brings you more and often better options for controlling sound, low-frequency sound isolation is an ever growing concern, a lot of older practices are all but abandoned, and low frequency sound isolation is an ever-growing concern in this world of home theaters and cars, trucks and things that make noise.
Orfield sees the changes happening and says, "Due to the growth of the home theater industry, there has been a lot more focus on performance-based products. As a result, more products are being tested than ever before to find out what actually works compared to what was thought to work.”
Sounds of Silence
Let’s take a look at some of the basic materials, constructions, techniques and products that are used in noise control.
Sound control discussions often being with the common wood stud wall, which is a poor sound barrier for two reasons: the combination of wood studs that rigidly connect the two sides of the wall, allowing noise to flow easily from one side to the other, and resonance problems that keep the performance of this wall type low.
Numerous techniques have been developed over the years to improve this performance.
Decoupled framing. Two effective ways to improve the sound isolation of a wall are to use staggered studs—2-by-4 wood studs offset on 2-by-6 top and bottom plates so that the two sides of the wall are connected only at the top and bottom—to improve sound isolation notably. Double stud constructions utilize two separate rows of studs with drywall on the outsides, forming a single large central air cavity. All things equal, double studs are the highest performance type of wall you can build due to the lack of any connection between the two sides of the wall.
The downsides to staggered and double stud constructions are lost floor space (particularly for the double stud constructions) and increased construction costs. A high level of sound control, however, is never free.
Resilient channel. Resilient channel is a flexible metal channel that helps improve sound isolation by mechanically separating the two sides of a wall. Resilient channel has some great aspects that make it an attractive solution. It uses a fairly minimal amount of floor space (typically about half an inch), it’s low in material cost, it’s readily available, and it can be effective. But its history in the lab and field has revealed some limitations as well. The product works by breaking the mechanical connection between two sides of the wall.
Things like an errant screw reaching a stud can restore the mechanical connection and substantially lower performance. This is called a short circuit. Additionally, not all channels perform the same. A variety of channels are being sold on today’s market, and they will not all perform as well as test data might imply.
Finally, resilient channel walls have not typically yielded great low frequency sound isolation—an increasing concern in the world of home theaters.
Sound clips. Sound clips, such as those offered by PAC International or Kinetics Noise Control, work in the same way as resilient channel, but offer higher performance. Additionally they space the drywall well away from the studs, greatly reducing the chances of short-circuiting your construction. Lastly, these products are manufactured to solid specifications, ensuring that you get what you want to get. The tradeoffs are a higher cost than channel, and the clips use considerably more floor space.
Both resilient channel and sound clips are maximally effective on single wood stud walls. They have some effect on staggered stud walls, which have some mechanical connection at the top and bottom plates, but are not effective on double stud constructions because double studs are already totally decoupled.
25 gauge steel studs. 25 gauge steel studs are intrinsically flexible and offer performance similar to resilient channel assemblies of similar depth. Heavier steel studs perform much more like wood studs.
Viscoelastic materials. Viscoelastic materials are a rapidly growing segment of the market, as advances in recent years in technology and availability have brought them to the mainstream.
Viscoelastic materials don’t work by decoupling, rather they work by converting mechanical vibration into small amounts of heat, damping resonances and dissipating sound as it travels through a structure. Viscoelastic materials generally have advantages when walls need to be kept thin, maximizing floor space, and are not subject to short-circuiting. Some viscoelastic materials have been shown to have a pronounced positive effect on low frequency sound isolation in addition to raising STC. Not all viscoelastic materials perform to the same level. Viscoelastic technology is available in the form of drywall laminated with viscoelastic from the factory, and one fully tested liquid viscoelastic product—Green Glue from the Green Glue Company—is also available.
Liquid damping materials are applied like any conventional adhesive between layers of drywall or subfloor during construction, and they dry in place to form the viscoelastic layer. Factory-laminated board, such as product available from Supress Products and Quiet Solution, can be very thin and can require only a single layer of board to be installed in the field. These advantages are countered by high prices and limited weight of the construction (weight is always an important factor). For the drywall contractor, liquid damping materials place more importance on their services (labor from an extra drywall layer) while keeping overall system costs low.
Insulation. Insulation of some type should be used in all constructions that wish to contain noise. Over the years a wealth of test data shows that common, inexpensive fiberglass routinely used in building is an excellent material for sound control.
Sealing the walls. Existing data suggest it is not important which sealant you use as long as you use a sealant, and use it competently. It is critical to the success of any sound control construction. Imagine loud music playing in a room with the highest performance wall imaginable … now imagine how much noise would pour out if you opened a door. This is very much like what will happen if seal quality is not tended to.
Importance of testing. It is critical that any sound control product you spend your client’s money on be thoroughly tested. A prudent manufacturer of noise control products will have an array of tests from an independent lab available to their customers. Preferably, these tests show the same construction (same studs, same insulation, same drywall) and also show test results with and without their product to highlight exactly what the product offers. You should strive to avoid using untested products because if it isn’t tested, then you simply don’t know what you’re getting.
Those are a few of the tools available to the contractor in the battle against noise. It is important to observe that no single product is "the best” choice. These different products and technologies each have applications in which they are a prime candidate, and others in which they are not.
These are some of the tools available to you in the battle against noise.
About the Author
Brian Ravnaas is the technical director for The Green Glue Company, Fargo, N.D. He also operates a "specialty coatings” R&D company.
For More Information
In support of this article, the Green Glue Company has prepared a Web page at www.greengluecompany.com/AWCI.php that will allow you to browse the topic of sound isolation to a greater degree than could be squeezed into this article. We also offer packets to contractors highlighting the techniques of sound isolation—sealing techniques, methods to help alleviate short circuiting problems in resilient channel constructions, and the pros and cons of our and other products.