Visitors to Willow Creek Ranch in Johnson County, Wyo., are awestruck when they first spot the “Red Wall.” This mountainous ridge protects the peaceful cattle-grazing valley to the west. Back in the Old West, the easiest way through the Red Wall was the narrow Hole-in-the-Wall pass. Outlaws like Jesse James and Butch Cassidy took advantage of this natural phenomenon.

Joining forces as “The Hole-in-the-Wall Gang,” this group of bad-men knew that the Red Wall gave them the most protection from intruders if they could just head ‘em off at the pass. Trite but effective.

Acousticians also talk about a “hole-in-the-wall.” Also called the “coincidence dip” or “critical frequency,” this hole-in-the-wall is the easiest way for noise to travel through most walls; a narrow band-pass at 3000 Hz. Today, a new hole-in-the-wall gang is taking advantage of this natural phenomenon. They know that walls give the most protection from intruding noise if they can just head it off at this band-pass.

Arguably the leaders in this new gang of companies are Kevin Surace and Marc Porat. Their company, Quiet Solution, Inc. of Sunnyvale, Calif., produces a new type of wallboard which is described in their freshly issued U.S. Patent.

Damping the bending waves

Technically speaking, the hole-in-the-wall phenomenon occurs when the wavelength of the bending waves in the wallboard equals the wavelength of the sound in air projected onto the wall and the waves coincide. Heading off noise here means either adding mass to the wall or damping the bending waves with some kind of shock absorber. Kevin Surace explains: “QuietRock products work through single or multiple constrained-layer damped systems. Rather than using mass, an internally damped panel flexes during vibration (when excited by acoustic energy) and shear strains develop in the damping layer. Energy is lost through shear deformation. By increasing the amount of damping, we are able to deliver panels that can be equivalent (acoustically) to eight or more layers of regular gypsum.”

(Although the projected one QuietRock panel to eight layers of regular gypsum may be technically correct, the statement, by itself, may be misleading. Careful comparison of the acoustical characteristics of the various wall composites considered, whether with QuietRock, regular sheetrock, or resiliently mounted sheetrock, is required to select the best option for each situation.)

Constrained-layer damping is simply a sandwich of something gooey between two panels. An Oreo cookie is a good example. You can twist the cookie apart, but the cream filling absorbs energy and slows things down. Not really a new concept, it was introduced in a 1939 British patent for damping vibrations in automobile body panels. QuietRock panels are multi-layered sandwiches, typically consisting of 1/4-inch gypsum on the outside and 30 gauge steel, 1/10-inch MDF (Medium Density Fiberboard), mass loaded vinyl or a combination of internal layers held together with a viscoelastic (gooey) glue.

Two other members of the new gang are Supress Products and National Gypsum Company. Supress’ Sound Engineered Drywall (SED) is also a multi-layered product; however, National Gypsum has taken a simpler approach in the design of their SoundBreak wallboard. Christopher Pinckney, product manager of Gypsum Systems for National Gypsum, describes their manufacture, “The board is manufactured by sandwiching a layer of viscoelastic damping polymer between two pieces of enhanced density, mold-resistant gypsum board. The higher density core provides increased mass and the polymer applied between them creates constrained layer damping. Both are key variables that directly impact the sound transmission loss through a wall partition.”

I asked the gang a few questions in order to compare panels.

W & C: How does working with QuietRock, SED or SoundBreak compare with working with regular gypsum board?

QuietRock: “Most of our products hang, score, and snap similar to regular gypsum boards and do not require any special tools or training.”

SED: “It’s the same as regular gypsum with snap-and-score features for easy installation.”

SoundBreak: “SoundBreak Gypsum Board is installed and finished like traditional gypsum board it can be cut by scoring deeply from both sides of the board before snapping, or with the use of a hand or power saw.”

(It’s probably safe to say that cut-resistant gloves are needed when handling any boards that contain sheet metal and that many of these boards are tough enough to require a power saw.)

W & C: What are the advantages of a QuietRock, SED or SoundBreak wall or ceiling compared with other sound rated assemblies?

SED: “Biodegradable, non-toxic, SED-AM (anti-mold) drywall can be used in new or existing structures. It scores and snaps easily, reducing labor costs and eliminating the need for any special tools, training or equipment for installation. Also, SED-AM’s suppressive features are not affected by exposure to the UV rays in sunlight, allowing builders to place panels conveniently on exposed sites. The SED AM panels provide an extra level of sound-proof quality in floors, ceilings and walls to meet the highest standard of noise suppression, up to STC 78+ performance with a one (1) hour fire rating from full scale ASTM testing. SED-AM also suppresses mold growth anywhere on the installed panels. The product’s non-metallic qualities ensure there is no interference with cellular reception or wireless networks and can be used in place of regular drywall or applied directly over existing drywall surfaces.”

SoundBreak: “The use of SoundBreak gypsum board results in cost effective wall partitions with high rated STC values that are thinner than traditionally built high rated STC wall partitions providing increased usable floor space. Because SoundBreak is installed like traditional gypsum board it offers a more reliable and less complicated solution to alternate methods requiring clips and/or channels.”

QuietRock: “Lowest total cost assemblies. Unlike older techniques (such as resilient channel) they cannot be shorted out during or after construction.

In most cases, choosing QuietRock can save significant money in the total assembly cost compared to double-studs (can reduce to single studs with QuietRock), clips or channels. Most builders choose QuietRock to save money as well as increase overall reliability of acoustic walls.”

(In a properly built gypsum board on resilient channel assembly, one leg of the resilient channel is screwed to the supporting structure and the gypsum board is screwed to the free leg of the resilient channel. Since the resilient channel is like a spring, the gypsum board is not rigidly attached to the structure, therefore vibration and noise is not easily transferred from the structure to the gypsum board. A nail or screw which is haphazardly driven through the gypsum and into a supporting stud or joist is said to short out the assembly since this is a rigid attachment. I’ve seen this problem mostly in projects where resilient channel was specified by someone that did not understand this danger.)

W & C: What mistakes should designers and installers be on guard against?

SED: “Installers must seal all penetrations or air leaks to ensure the best sound suppression.”

QuietRock: “QuietRock does not need to be floated. It can touch surrounding walls without any degradation in performance. So the issues typically revolve around flanking paths, as in all acoustically rated wall systems.

These can include outlet boxes, heating vents, plenums, adjacent walls etc.”

SoundBreak: “When specifying any high STC wall partition, sealing perimeter gaps and wall penetrations is crucial to performance. We recommend leaving a 1/4-inch gap along the perimeter to be sealed with an acoustical sealant or caulk. In areas around outlet boxes sealant and putty pads are recommended.”

(This is a point of contention for any sound rated wall or ceiling: can you finish the corners with mud and tape without hurting the noise isolation?

Acousticians typically require a ¼-inch perimeter gap which is then sealed with a flexible caulk. Architects want to keep things simple with mud and tape. Until I see authoritative test data that says otherwise, I’m keeping the gap.)

W & C: How many QuietRock, SED and SoundBreak panels will be installed this year? What is the projected growth?

QuietRock: “Over 1M (million) panels will have been installed by year’s end, and the popularity has been doubling annually for five years.”

SED: “We’ll sell literally millions of square feet this year with double digit growth next year.”

SoundBreak: “National Gypsum is a privately held company and does not report this information.”

(To be fair, SoundBreak was just introduced at the INTEX EXPO 2007.)

W & C: What states are the leaders in using QuietRock, SED or SoundBreak?

SED: “Any state with large urban areas. We sell mostly to New York, Illinois, Florida, Texas and California.”

QuietRock: “QuietRock products are used throughout North America. There is no particular geographic concentration.”

SoundBreak: “Sound damping has become increasingly more important in both residential and commercial construction. While not specific to certain areas of the country, our success has been more specific to the type of construction such as high rise condominium growth, high end hospitality, health care, education, townhouses, and home theaters.”

W & C: What grades of QuietRock, SED and SoundBreak are available and how is each one selected?

QuietRock: “QuietRock 510 1/2-inch is the lowest cost acoustical drywall product on the market today with an MSRP of $39.95 per 4x8 panel. QuietRock 516 is an upgraded version tuned specifically for 16-inch OC wood studs in traditional single family homes. QuietRock 525 5/8-inch product is our popular one-hour fire rated, Type X, UL classified product for wood and steel studs. QuietRock 527 5/8-inch was designed specifically for Dietrich’s new UltraSTEEL studs for commercial use. It is also one-hour fire rated, Type X, UL Classified.

QuietRock 530 5/8-inch product is type X UL classified and used for acoustical as well as shear requirements. QuietRock 545 is a 1 3/8-inch THX certified product for extreme performance tested to STC 80.”

SoundBreak: “SoundBreak is 5/8-inch thick and currently available in 8-, 9-, 10-, and 12-foot lengths.”

SED: “Supress Sound-Engineered Drywall, 4’ x 8’ panels are available in the following thickness:

1/2-inch-Remodel /Upgrade from Apartment to Condo specs; 5/8-inch-New Construction/Remodel/ 1/2-inch-Remodel /Upgrade from Apartment to Condo specs; 5/8-inch-New Construction/Remodel/Commercial Upgrade; 3/4-inch-Home Theater/Conference Rooms/Medical Facility (HIPAA)/Music Rehearsal Areas; 1-inch-Professional Recording Studio/Digital Theater/Concert Hall.”

W & C: What is the best way to design an assembly using QuietRock, SED or SoundBreak?

SED: “Reduce the number of penetrations as much as possible. It’s most important to seal all air leaks and seams. A great quality about Supress Product is the ability to do patch work or start an entirely new product. Many existing buildings only require minimal work to eliminate noise. But we’re working with numerous builders and architects to incorporate soundproofing throughout the entire building. So it really depends on the level of noise reduction that is required per project.”

QuietRock: “QuietRock products are used in single, staggered and double stud assemblies.”

SoundBreak: “SoundBreak Gypsum Board is UL approved as an additional layer on one or both sides of fire-rated wall assemblies such as UL U465.”

The new Hole-in-the-Wall gang seems to have effectively used constrained-layer damping to cut off noise at the band-pass. By closing up this one easy route, the wall can now be as formidable a barrier as it should have been in the first place. Unwanted intrusions are shut out, and the sun can set on the peaceful valley beyond.