Delivering acoustic sanity

by brittney_cutler | December 29, 2021 11:11 am

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By Bill Devin

Urbanization is increasing. According to 2018 United Nations forecasts, seven out of 10 people will live in cities by 2050. Faced with a huge shortage of space, mixed-use concepts bring high-density tower blocks and space-saving neighborhood developments to life. However, maintaining quality of life and longevity in proximity to living, working, and leisure activities relies critically on specifying the right acoustic solutions.

The World Health Organization (WHO) reports noise pollution as only second to air pollution in detrimental environmental health factors. In the post-COVID era of working from here (WFH) people are seeking live-work environments. Acoustics and building sound isolation become not only critical to the success and long-term viability of a development in this era, but also the only humane ways to build in cities where people will be living and working in the same building.

According to WHO, excessive noise disturbs sleep, causes cardiovascular disease, and has psychophysiological effects, such as reduced performance, elevated irritability, and changes in social behavior. Medical research has found the need to cope with exposure to excessive or incessant noise increases the risk of high blood pressure, stroke, and heart attack, so it makes sense that building materials covering broad strokes would help to mitigate noise and protect the comfort level of its occupants.

“Poor acoustics is that silent killer. Think about distractions in your office—or home office,” says Sara Hickman, sustainability director at RDC-S111 in Long Beach, California. Hickman is a LEED AP, WELL AP, and EcoDistricts AP. “Poor acoustics can be so abrupt, and when distracted by something abrupt, it really throws you.”

She suggests focusing on typology, codes, and zoning when specifying effective acoustic solutions.

“In the end, they do bring a lot of value because of the rationale behind them.”

The post-COVID era has birthed the Zoom Generation and, with it, a real estate trend the Wall Street Journal has referred to as “Zoom Towns.” These new Zoom Towns—typically located in smaller, secondary markets—are organizing to become the new 10-minute city. In other words, a metropolis where residents live a hybrid life: working, sleeping, shopping, and entertaining within the same development or neighborhood.

In denser cities, usable real estate is at a premium, so density is increasing. As usable real estate decreases, developers are buying less-desirable properties that abut public transportation or finding historic buildings, such as old mills, which can be skillfully re-used by developers who hire firms known for their mastery of historical renovation.

In each case, wise developers select premium building acoustic products to address their future tenants’ acoustic sanity. This contributes to the building’s value, long-term viability, and ability to retain tenants. Sound acoustics product specification also future-proofs a building faced with possible transit developments years down the road.

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RDC-S111 designs a lot of multi-family and affordable housing, which tends to be located right next to public transit and major freeways.

“We’re constantly thinking about acoustics as early as conceptual design and asking, ‘What are we doing besides specifying high-performance glass that may or may not be value engineered out?’” relates Hickman.

When it comes to multi-family building acoustics, Hickman advises having an acoustical engineer on board to model and recommend an appropriate roof composition, and for architects to specify robust wall assemblies.

In its latest newsletter, Dialogue Now, Gensler predicts the work from home trend in a post-COVID era is here to stay. This may have residual effects on residential design, such as the need for an effective home office. In a WFH situation, the Four Work Modes—focus, collaborate, learn, and socialize—still apply and need to be addressed by the space, according to Gensler’s Tom Steidl and Brooks Howell.

“Multi-family residential buildings will need to be rethought, both in terms of dwelling units and communal amenity areas.”

The duo explores how to do this, while still addressing these four modes by considering real-life WFH situations. How to focus when kids are home? How to collaborate effectively on video calls when trying to hide a pile of dirty dishes in the background? Is a laptop propped up on a milk crate on the dining room table truly an ergonomic workstation?

As for non-children, pet, and spouse noise falling into the category of “Other,” Gensler’s workplace study points to research from the University of Illinois, which found a high level of noise (85 dB and above) reduces information processing and hurts creativity. Moderate ambient noise (70 dB) introduces enough stimulus to promote abstract processing and imaginative thinking. Three of Gensler’s 10 workplace acoustics strategies also apply to the planning, design, and construction of mixed-use environments in the post-COVID era of WFH: zoning, sound absorbing, and walls. These three strategies also correspond to the General Service Administration’s top three acoustic parameters used in acoustical design specifications: background noise, noise isolation, and sound absorption[3].

“As human beings we take care of things when it affects us, and there are so many noises at home: leaf blowers, lawn mowers, garbage trucks, even barking dogs,” says Sayali Wazalwar, acoustics researcher and specialist at GBBN Architects. “No matter what, these noises affect us especially in our WFH environments.”

Wazalwar offers several recommendations to remediate these unfortunate distractions. First and foremost, she says, be intentional in plans to use each space and organize adjacencies accordingly. In a home, examine the average level of sound, and have one declared ‘focus’ area in the home. Plan where doors are located with respect to those opening into a quieter area. Sealing a closed door, especially avoiding the gap under the door, will help to stop noise, suggests Wazalwar.

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Throughout the core and shell, she suggests using double pane windows with gaps and sealants to absorb excess sound from exteriors. She also suggests creating an air gap in the wall cavity to discourage noise transfer from spreading downward into neighboring units. For instance, decoupled elastic false walls provide a reliable solution to effectively reduce airborne noise between rooms. Use drywall clips to stop structure-borne noise bridging the drywall and the false wall. Excellent building acoustic values can be achieved with these easy-to-install rubber and metal fasteners—even where little wall mass is available, such as a multi-family high-rise.

Another effective acoustic solution involves a dimpled flooring underlayment made from recycled tire rubber. It is designed to reduce the transmission of impact sound generated by footfall noise and is commonly used underneath solid and engineered hardwood floors, concrete, screed, and floating floor systems. It is available in multiple standard thicknesses (6 mm, 8 mm, 10 mm, 17 mm, and 25 mm [0.24 in., 0.31 in., 0.39 in., 0.67 in., and 0.98 in.]) which can be selected based on the application. Specifying this type of sound isolation material in the floor-to-ceiling assembly offers architects and acoustic engineers an advantage when it comes to design and structural flexibility and guarantees residents complete serenity.

Finally, advises Wazalwar, avoid noisy HVAC systems by using larger ducts to decrease air velocity, therefore making less noise. It is also important to properly treat all noise and vibration at its source. For instance, mechanical equipment foundations should be properly isolated to ensure peace and comfort in adjacent units. Vibration isolation materials provide damping, decoupling, mass, and absorption. A high-performance elastomer or a high-performance mixed-cell polyurethane is often specified to protect residents from rooftop mechanical vibrations. Additionally, these products offer the ability to create customized solutions which allow reliable planning and ensure the exact amount of material required can be precisely specified by acoustic engineers. A panelized floating subfloor system may also treat mechanical rooms for impact sound insulation. It absorbs airborne sound and dissipates structure-borne noise and vibration.

Many developments position themselves to attract residents with ready access to mass transit. However, this creates a challenge for the developer and owner to ensure they design and deliver the high-level acoustics needed to keep residents shielded from noise and vibration caused by this kind of amenity.

At 121 E. Route 66, a 198-unit mixed-use development in Glendora, California, the construction uses high-performance floating floor vibration isolation products to neutralize primary noise sources while also allowing for a thinner slab. Building acoustics products mitigate noise and vibrations with their low natural frequencies (f ≥ 7.5 Hz), which are constant over wide load ranges and can be installed in multiple layers. The high-performance floating floor shields residents from noise pollution in the form of vehicle traffic and the adjacent freight railroad, and future-proofs the building to ensure residents are protected from additional noise pollution associated with the proposed extension of the Metro Gold Line.

A mixed-use project in a similar situation, in Berlin, Germany, with train tracks running through the basement of the building uses a high-performance elastomer made of rubber fibers, granules, and polyurethane to isolate residents from any disturbances. This material is available from manufacturers in rolls or sheets. High-quality manufacturers offer it in eight unique types, each for a specific load range. Premium types are supplied with a dimpled underside to decrease the dynamic stiffness and to provide an air gap. This kind of building acoustic technology allows urban planners and developers to confidently invest in real estate previously thought of as unfit for building with properly designed and specified building acoustics.

The renovation of the historic Water Street Mill complex in Williamstown, Massachusetts, included converted restoration of abandoned properties into a revitalized mix of lofts, apartments, and condominiums. Finegold Alexander Architects designed the interiors of 61 housing units for Cable Mills—13 of them designated affordable. The directive for all of them was to utilize highly sustainable, energy-efficient, and eco-friendly systems and materials. They specified a cost-effective, dimpled flooring underlayment made from recycled tire rubber to provide the best acoustic experience for all  Cable Mills residents.

Future-proofing mixed-use and multi-family, or renovation and re-use developments for acoustic sanity in the post-COVID world is only half the battle. Hickman reminds that in order for multi-family projects to weather the value engineering (VE) process, specifiers must be strategic in finding integrated solutions to offer a triple bottom line.

“Good solutions make sense on every level,” agrees Wazalwar.

For instance, specify an economical product offering acoustic buffering and thermal conservation benefits.

“Acoustic comfort is huge,” says Hickman. “And I feel like it’s been the unsung hero for a very long time. [Good] acoustics is a quiet but efficient design strategy.”

Author

Bill Devin has been a business unit manager at Regupol America since 2014. He has over 30 years of experience in the acoustics field, with the last 20 years in multi-family acoustic design. He has been involved in many prestigious projects and works closely with architects, contractors, and developers in product selection to ensure the highest acoustical ratings and overall customer satisfaction. Bill currently lives in Massachusetts and enjoys woodworking, gardening, and meeting new people.

Source URL: https://www.constructionspecifier.com/delivering-acoustic-sanity/

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