feature

by Steve Saarman

Noise control in multifamily residential buildings has a significant impact on people’s experience of privacy and wellbeing. It is the unwanted sound or noise, especially at inappropriate hours, traveling into units that is the most irritating and often the most difficult to control: loud music and voices, blaring radios and TVs, ringing phones, slamming doors and clattering garage door openers, not to mention the cycling sounds produced by kitchen appliances like refrigerators, dishwashers, microwaves and ventilation fans. We are also subjected to the irritating sounds of water pipes banging or flushing, heating and air conditioning fans humming and vibrating, garbage dropping down chutes and metal stair cases shuttering under hurried feet. It can all be overwhelming and deleterious to our nervous systems.

Additionally, our ears must also process and manage external noise sources such as airplanes, ambient auto traffic, sirens, construction, lawn mowers, leaf blowers and barking dogs, just to name a few. Where is the peace and quiet?

Baseline noise levels continue to increase and we must find solutions. Looking at the big picture, solutions are evolving on many fronts: social, technological and physiological. Obviously, populated living in urban environments is the path of our future. Spread-out suburbia (which is based on inexpensive gas to support commuting), in which every family has their own home and backyard, is no longer viable. It will devolve and change into newly aggregated urban centers that must support people in their immediate areas. Therefore, the trend will be towards taller multifamily buildings.

Technologically, there has been a huge information push by the construction industry, in both new construction and remodeling, to understand and improve the performance of buildings through new materials that support sustainable construction while enhancing quality of life. This is one part of the solution to higher density living.

There are many proactive remodeling strategies that can help control unwanted noise. First, we will start with an understanding of what sound is and how it differs from noise, some pertinent technical terminology, the types of sounds and their pathways though a building’s structural systems and what “flanking” is, before we move on to the fun stuff—new sound abatement technology.

Sound is actually waves of energy that travel from the sound source through air, water or solid objects. When sound vibrations or generated waves strike our eardrums, they vibrate and correspondingly create our “hearing” experience. The pressure level that a sound wave exerts when it strikes a surface is measured in decibels. Therefore, the larger the vibration, the greater the sound pressure level and the louder the sound heard by our ears. Noise is defined as “sound that is unwanted and a disturbance to our well being.”

Know Your Rating Systems
Construction products are often given Sound Transmission Class ratings. It is a measure of the airborne sound transmission loss through wall or floor/ceiling assemblies, or through doors and windows. The higher the STC rating, the better that product will perform at dampening sound.

Impact Insulation Class is a measure of how noise from an impact sounds. Floor/ceiling assemblies are additionally rated in this manner. For example, there are ICC ratings on how the impact sound of footsteps carries through different floor/ceiling assemblies. This rating is very helpful in selecting appropriate flooring material to help mitigate noise traveling between different rooms or units. Other common impact noises are generated from dropped or sliding objects, or banging, often heard as dull thuds through the structure.

Both airborne and impact sounds share some things in common, but impact transmission is much more difficult to measure and control. This makes it difficult to create reliable rating tables for designers. How impact noise is perceived after being transmitted through a wall or floor depends on so many factors. For example, what is the object striking the surface and what is the force of the blow? How rigid is the building assembly being struck and how resilient is its surface? Each will influence the resulting perceived sound. Different standard wall and floor/ceiling assemblies have been tested and have received STC ratings. This is very useful to designers.

Unfortunately, a good STC rating for airborne sound does not necessarily provide acoustic privacy for an impact sound. Reducing impact noise requires different construction assemblies. For example, many wood-framed multifamily buildings utilize “gypcrete,” a cement-like topping, over the plywood subfloor. This assembly has a high STC rating, but can actually amplify impact sound coming through the floor. Consequently, in order to lessen the impact sounds, a cushioning material must be added on top of the plywood to separate the concrete topping.

Sound can “get around” a highly rated wall or a floor/ceiling assembly. This is called “flanking.” The tricks to create highly rated assemblies are well documented, but how a wall connects to other walls or between the upper and lower floor/ceiling assemblies is often the weak link during construction. Sound waves can literally travel between the bottom of wall framing and across the subfloor to the room on the other side. The same flanking path is followed at the corners of a room and also at the wall/ceiling corners. If the drywall is gapped at least a quarter-inch at the corners and then filled with a continuous bead of acoustical caulk, so each room plane or wall/ceiling assembly is separated and can function acoustically independent of each other, flanking is mitigated and the separate assemblies perform as designed. This technique of isolating room planes is called “decoupling.”

Sound-Dampening Upgrades
Most buildings that are wood framed are built to standard code-required STC ratings. Sometimes it is the goal to increase these ratings to create a quieter and more marketable living space. The three main ways to control unwanted noise or sound vibrations are: increase the mass of the partitions; break the path of vibration (by using caulk or a resilient channel); and increase cavity absorption (usually by adding insulation).

Designing more efficient wall and floor/ceiling assemblies continues to evolve with new products that still utilize the “breaking the path of vibration” practice. QuietRock (www.QuietSolution.com) and Supress (www.supressproducts.com) lead the way in engineered drywall. These products range from a 50% to a 200% increased STC rating over one layer of standard drywall, with little chance of workmanship error in installation.

Higher STC-rated walls or ceilings have traditionally used resilient channels, which are strips of sheet metal fastened across the framing, sandwiching the framing and drywall and separately attached to each. This method of installation breaks any direct fastening contact between the materials, thereby intercepting the sound vibration path. Unfortunately, workmanship installation error can “short circuit” these assemblies. A new more fail-safe system for decoupling is the Resilient Sound Isolating Clip (RSIC-1) by PacInternational (www.pac-intl.com), which utilizes neoprene washers below a metal grid system. It increases any assembly rating by 15 to 20 STC points!

It is also possible to suspend an entire metal ceiling grid on a series of spring brackets to further significantly increase its STC rating, but the grid must be installed with an acoustic caulk bead around the entire perimeter. This company also makes acoustically isolated wall brackets for flat screen TVs, isolation hangers for garage door openers and spring isolators for rooftop-mounted equipment. The RSIC-1 also performs much better at
lower vibration frequencies (like the boom from base speakers) than the old resilient channel.

Penetrations in a wall or ceiling assembly can destroy its STC rating. All electrical boxes must be enhanced with puddy pads. Knauf Puddy Pads (www.knaufdrywall.co.uk) install on the inside of electrical boxes, making them cost effective for retrofit situations. If possible, it is important to refrain from using can lights in a ceiling, because they are costly to address acoustically, and from a fire safety point of view. Track lighting offers many great options without
the trouble of building a fire-rated drywall box to enclose the can light and then seamlessly integrate it back into the ceiling for acoustic continuity.

For windows and doors with special acoustic needs, Milgard (www.milgard.com) has created the Quiet Line Series of vinyl windows, which have worked very well on some of our projects. Another option is to replace a window’s existing glass
with dual glazed laminated glass. This provides both UV protection and added acoustic performance.

Gypcrete-type concrete toppings are still a good acoustic isolator, especially when coupled with impact isolation material such as Acousti-Mat (www.maxxon.com), AcoustiCork (www.AcousticCorkUSA.com), which is a naturally sustainable product, or recycled rubber padding by Regupol (www.regupol.com), just to name a few.

Acrylonitrile Butadiene Styrene waste lines and copper water supply lines can often be noisy, usually due to improperly broken path vibrations with the framing. Copper pipes should always use acoustic isolators instead of directly touching framing, along with water hammer extensions at each outlet. ABS waste lines are thin and noisy, while cast iron pipes are the quietest, but more costly to install. ABS pipes can be wrapped with Lawry’s Duct Wrap Tape to muffle noise, if they are not replaced.

In dealing with extreme outside airborne noise, building up the exterior walls with increased dense mass (like stucco, stone, or brick), wall cavity insulation, a superior performing interior drywall system and sound windows is a good first move to deal with this issue. If outdoor space allows, additional options are solid masonry fences or landscaping berms (mounds of dirt) installed between the building and the noise source.

Communication Is Cheaper Than Remodeling
All of these upgrades will certainly help decrease the noise in and around your multifamily building. But a helpful first step is social adjustment and consideration of one’s ambient noise. Managing social noise involves cooperation between neighbors and utilizes clear, calm communication when bringing up issues or concerns. Often, people lack awareness of the noise their children, pets, music or voices generate.

It is necessary that neighbors communicate with one another about their needs and preferences in terms of noise levels and timing of noise. Coming to general agreements when certain activities can or cannot be executed is important. If conscientiously worked on, ultimately a list of rules and a code of conduct can be created for everyone’s benefit.

 

---

The opinions expressed in this article are those of the author, and do not necessarily reflect the viewpoint of the SFAA or the SF Apartment Magazine. Steve Saarman is with Saarman Construction, Ltd. Copyright © 2008 by Black Point Press. All rights reserved.