Sound Advice A Guide to Acoustics
Published by Kenilworth Media Inc. 15 Wertheim Court, Suite 710 Richmond Hill, Ontario L4B 3H7 Toll-free: 800-409-8688 (905) 771-7333; Fax: (905) 771-7336 www.constructioncanada.net
The information and contents in this publication are believed by the publisher to be true, correct, and accurate, but no independent investigation has been undertaken. Accordingly, the publisher does not represent or warrant that the information and contents are true, correct, or accurate, and recommends that each reader seek appropriate professional advice, guidance, and direction before acting or relying on all information contained herein. Opinions expressed in the articles contained in this publication are not necessarily those of the publisher.
Š 2015 Kenilworth Media Inc. All rights reserved.
Contents Part One Contract Administration for Acoustics
5
By John O’Keefe, M.Sc., P.Eng., FIOA, and Kiyoshi Kuroiwa, B.A.Sc., P.Eng.
Part Two Planes, Trains, and Automobiles
13
By Cliff Faszer, P.Eng.
Part Three The Green Soundscape
21
By Niklas Moeller, MBA
Part Four Studio Sound
31
By Oliver Barkovic, B.Eng.
Part Five Sound Attenuation for Piping Systems By Tim Meadows
4
CONSTRUCTION CANADA ACOUSTICS
41
Part One Contract Administration for Acoustics
BY JOHN O’KEEFE, M.SC., P.ENG., FIOA, AND KIYOSHI KUROIWA, B.A.SC., P.ENG.
John O’Keefe, M.Sc., P.Eng., FIOA, principal with Toronto’s Aercoustics Engineering Limited, is regarded as one of Canada’s foremost architectural acousticians. He is responsible for the acoustic design of many performing arts centres, such as Vancouver’s Orpheum and Queen Elizabeth Theatres, the Esplanade Arts and Heritage Centre in Medicine Hat, Alberta, and Toronto’s Princess of Wales Theatre. O’Keefe can be contacted by e-mail at johno@aercoustics.com. Kiyoshi Kuroiwa, B.A.Sc., P.Eng., created and leads Aercoustics’ contract administration department. He is responsible for the acoustic design and contract administration of architectural projects such as the Aga Khan Museum and Ismaili Centre in Toronto, Simon Fraser University School for the Contemporary Arts in Vancouver, and Mount Allison University’s Purdy Crawford Teaching Centre in Sackville, New Brunswick. Kuroiwa has applied his experience playing piano and percussion in orchestras to the acoustical design of projects. He can be reached at kiyoshik@aercoustics.com.
5
CONSTRUCTION CANADA ACOUSTICS
Photo Š Larry Goldstein
Contract Administration for Acoustics A building is an assembly of various materials intertwined to construct something solid and enduring. However, even small adjustments in a building’s plan can lead to unforeseen problems, especially to acoustics and noise control performance.
6
CONSTRUCTION CANADA ACOUSTICS
John O’Keefe and Kiyoshi Kuroiwa are next to a scale model used to design performance spaces, one of the many project types that can benefit from acoustical contract administration services. Photos courtesy Aercoustics Engineering Limited
Acoustics and ambient noise are common complaints, but relatively small changes can have big acoustical implications. For example, while moving a wall to a different location may seem like an easy revision in the building stage, this can cause a troublesome echo that has a snowball effect on the floor’s acoustics. Governed by the laws of physics, acoustics is a science that either helps or hinders the ability to clearly hear sound. From too much ambient noise to too much echo, there are many things that can go wrong acoustically in a building under construction. The science of architectural and environmental acoustics has advanced, and they have been incorporated into the design of projects. While these advancements have come a long way to influence the design process, there are still numerous ways to compromise the acoustic design. Sometimes, noise control and acoustics can be restored after the building is finished, but usually at a steep price. The positioning of lights or the adjustment of door seals can easily be changed post-construction; however, noise control elements are often hidden. This means correcting the problem usually requires breaking down walls to locate the source. This can add time and complications, as well as put a strain on budgetary requirements for the owner or contractor. Post-construction hassle can be avoided by having contract administration handled by someone with an acoustical background. Careful review of the contract requirements and onsite inspections at key points during the construction process help maintain the design’s acoustic integrity and ensure the ultimate acoustic goal is achieved. If possible,
7
CONSTRUCTION CANADA ACOUSTICS
one should consider adding a section in the specifications stating a start-up meeting is required to outline expectations and review acoustical mockups.
What is contract administration? Every construction project should include all specifications and details in its drawings and contract administration ensures all these details are followed. From an architectural standpoint, contract administration is not a new concept. However, contract administration for acoustical design has only recently become part of the mix. In the past, acoustical engineers would only provide the design, while architects (in conjunction with the mechanical engineers and other team members) managed the contract administration. Whenever room acoustic questions would arise postconstruction, acoustical engineers would be unable to provide immediate answers to the problem because they were not part of the construction modification process. Additionally, acoustical designs are increasingly more complicated and applicationspecific. As the complexity increases, most engineers and architects do not have the expertise to understand all the details in order to make the correct modifications to acoustical designs. As a result, most acoustical firms are seeing the benefits of assigning a specialist to oversee contract administration. There is great value in having a single person oversee the design’s implementation. This individual is dedicated to ensuring design ideas are realized, and devoted to catching contract administration issues. He or she should have a solid understanding of the design and its intended integration so executive decisions can be made on the spot to modify the plan, while still achieving the original acoustical goal. It should also be noted every project can be a learning opportunity because what did not work in one building still yields tremendous learnings for future projects. No matter how thoughtful the original design, the reality of site conditions may not always be conducive to the plan and modifications required. Whether the design does not suit the conditions onsite, or the contractor requests modifications, the contract administrator takes the design intent and distills it to figure out how to make the changes work for the conditions. There are always two questions to answer: what should be done, and what can be done. The answers may differ greatly and help identify what contractors will be amenable to doing when considering budgets and timelines.
Educating contractors With any construction project, time is of the essence. When the deadline is approaching and there is plenty of work to be done, some contractors may be faced with the need to make executive decisions based on what they know to complete the project on time. Unfortunately, due to a lack of understanding about acoustics, a seemingly small and quick design change may have a big impact on the final acoustical outcome. For this reason, one of the most important roles of a contract administrator is education. First, it is important to note that on the jobsite there are various terms and treatments with which contractors might not be fully familiar—such as acoustic door seals or vibration isolation. The contract administrator can translate the terms and provide information on how these treatments can be used to create an acoustically sound building. Second, there are myriad misconceptions about acoustics. The contract administrator can clear up confusion and ensure all parties are aware of how a design change will
8
CONSTRUCTION CANADA ACOUSTICS
Although the automatic door bottom was installed in these projects, it was not adjusted to drop when then door is closed. Sound is able to pass through the gap in the bottom, reducing the intended sound isolation.
have an impact on acoustics. A common myth is glass fibre in walls absorb sound. However, glass fibre is not the agent that absorbs the sound. Rather, it is the enabler in the wall to help block out the sound, allowing the wall to have a better acoustical performance. This is just one of many misconceptions that can lead acoustical plans astray. Having a contract administer available to answer contractor questions will ensure the right directions are relayed to the subcontracted tradespeople working on a project. By providing both expertise and education, the goal is to help contractors understand the importance of acoustics and how changes to the design may impede the acoustic goal. Compromised acoustics ultimately end up being costlier, so preventing issues before they happen is key.
9
CONSTRUCTION CANADA ACOUSTICS
The wall above the finished ceiling was not completed here, leaving a large hole in the assembly. While not visually apparent, the hole decreased the speech privacy of the meeting room, resulting in user complaints.
Working with you not against you During one of the first site visits, the contract administrator should sit down with the contractors and heads of trades, including drywall, mechanical, and masonry. The meeting should walk everyone through the design and identify where acoustics can be impacted. This includes discussing what can be seen in the design, and what is not as obvious—aspects like conduits in walls are not always visible on the drawings. While most contractors understand conduits need to be run in the wall, they do not take into account the acoustical reasoning of how to run an electrical conduit so it does not affect the wall’s acoustical separation. The separation is solid when there are two one-sided walls; but this acoustical separation will be lost as soon as a conduit is placed across two studs. To make a good acoustic wall, the design should have one wall move but not the other. This is because once a pipe is placed in between and screwed tight, both walls will move together and the acoustic benefit is lost. If the construction crew is aware of this beforehand, or if a contract administrator catches it during construction, potential problems can be avoided. Once the walls are covered, they will need to be opened up to uncover any issues, leading to the potential that elements will need to be rebuilt. This consideration is particularly important in condominiums. According to the Ontario Building Code (OBC), they have to satisfy a sound transmission class (STC) rating of 50. By implementing contract administration throughout the project, a
10
CONSTRUCTION CANADA ACOUSTICS
In this example, the mechanical and drywall installations were not co-ordinated. As the hanger was installed first, the drywall was installed around the hanger, creating a hole which allowed excess noise to the adjacent room.
contractor can ensure the minimum requirement is met and nothing needs to be redone once the building is occupied. Most contractors take pride in their work and strive to ensure buildings are solid. Acousticians want portions of the building to be flexible, and this needs to be communicated to an entire project team. However, this should not be perceived as a battle between the various parties involved in a construction project. It needs to be a collaborative effort whereby working together, both parties may find a better way to implement the design and reach the acoustical goal.
From paper to reality In order to have an acoustically sound building, it is imperative the various treatments be outlined in the contract. Contract administrators can only administer what is in the contract. By having a detailed plan including the acoustical treatments, it will help make certain the intended vision is realized. For example, when referring to vibration isolation, contract administrators will not only watch to ensure a contractor uses 25- or 51-mm (1- or 2-in.) springs, they also need to ensure the load on the spring is adequate to ensure it works properly. A spring with a 45.5-kg (100-lb) rated load, being loaded with only 13.6 kg (30 lb), would not be appropriate. However, a spring loaded at its rated load would provide the maximum benefit. Architects, contractors, tradespeople, and building owners should consider the following three tips regarding contract administration.
11
CONSTRUCTION CANADA ACOUSTICS
This transformer has been installed with a thin neoprene pad instead of the required spring vibration isolators, allowing vibration to pass into the structure, and enabling it to be heard in other parts of the building.
1. Write it down: If an acoustically sound building is the goal, everything needs to be outlined in the contract. It is difficult to administer a project and make recommendations if it is not included in the initial scope or budget. Suggesting additional work to facilitate good acoustics will require an increased budget, and possibly delay a project. 2. Trust and understand the acoustical consultant: Everyone involved in a project has an area of expertise. Avoid misconceptions of what acoustics involves, and take advantage of any tutorials offered to learn the basics in order to ensure the entire vision is achieved. 3. It is a two-way relationship: With so many people responsible for completing a construction project, pressing timelines, and limited budget, it is imperative to know where to give and where to take. The design team, contractor, and contract administrator must work together to understand all points of view to find a solution to any issues.
Conclusion Ultimately, acousticians strive to have someone walk into a building and have no idea an acoustician has been there. Success is having acoustics completely integrated into the design of the building so its effects can be enjoyed but not seen. This cannot be accomplished by acousticians alone. It requires significant collaboration between the architects, contractors, engineers, designers, and contract administrators, as well as building owners, to yield a finished product satisfactory to everyone involved.
12
CONSTRUCTION CANADA ACOUSTICS
Part Two Planes, Trains, and Automobiles
BY CLIFF FASZER, P.ENG.
Cliff Faszer, P.Eng., is the president and founder of Calgary-based FFA Consultants in Acoustics and Noise Control Ltd. He has been an acoustical consultant for 35 years. Faszer is a member of the Association of Professional Engineers, Geologists, and Geophysicists of Alberta (APEGGA), the Association of Professional Engineers and Geoscientists of British Columbia (APEGBC), the Canadian Acoustical Association (CAA), and the American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE). He can be contacted via e-mail at cfaszer@ffaacoustics.com.
13
CONSTRUCTION CANADA ACOUSTICS
Images courtesy Calgary Science Centre Society
Planes, Trains, and Automobiles Developing noise isolation for Telus Spark: Calgary’s new science centre After 44 years at its 11th Street SW location, Calgary’s science centre moved due to a lack of expansion space in 2011. The new Nose Creek Valley site allows room for a facility that is double the size, and has room for expansion. However, the new site presented challenges for designers. It is in line with the main north-south runway at the Calgary International Airport, and the planes that land heading north fly over the site at a low altitude. The location is also adjacent to Deerfoot Trail—a major freeway route through Calgary, and the Canadian Pacific (CP) Rail line. A right-of-way for a future light rapid transit (LRT) line is also located immediately adjacent. To meet owner requirements and exceed minimum noise isolation requirements, the building envelope needed to provide sufficient noise isolation from all these noise sources.
14
CONSTRUCTION CANADA ACOUSTICS
The science centre atrium clerestory glass installation on November 8, 2010. The interior light of all exterior insulating glazing was upgraded to 6-mm (0.2-in.) thick laminated glass to increase insulation from outdoor noise.
An interior view of atrium clerestory glazing.
The facility, officially known as Telus Spark: The New Science Centre, opened October 29, 2011. It includes: • numerous gallery spaces; • Dome Theatre; • Presentation Theatre; • classrooms; • large central atrium space; • lobby; • cafeteria; and • various support/administration areas.
Aircraft noise isolation The new location is in the airport vicinity protection area and, at a minimum, must meet the requirements outlined in Alberta Building Code’s (ABC’s) Division B Part 11, “Exterior Acoustic Insulation,” for noise isolation properties of the exterior building
15
CONSTRUCTION CANADA ACOUSTICS
The Dome Theatre’s structural steel installation as it appeared on December 14, 2010.
envelope. The protection area is a designated zone around the airport where there has been noise exposure forecast (NEF) contours determined. These are concentric lines around the airport runways that provide an indication as to the average energy equivalent noise level at a distance away from the runway. Higher NEF values are located closer to the runways, with the values decreasing as they move away. The first step was to determine where the building site lies with respect to the noise contours. The science centre is situated on the 35 NEF contour. ABC Chapter 11 outlines the acoustic insulation factor (AIF) that must be met by the building envelope based on the site’s NEF contour value––a site located in a higher NEF zone requires exterior building envelope assemblies with higher AIF ratings. Another factor that was considered related to acoustics insulation is the use of the building’s rooms. For example, spaces used for sleeping required a higher AIF rating than a meeting room. ABC provides AIF values for various exterior wall, window, and roof assemblies. Additional AIF values can be determined from sound transmission loss values of tested assemblies. The other variables determining the required AIF value were the amount of exterior wall and window area compared to the floor area of the room, and the number of different exterior wall components making up the room’s exterior envelope. The rooms with the highest AIF requirement in the facility are the classroom areas and those used for teaching purposes––such as the Presentation Theatre and the Dome Theatre. The gallery spaces did not require as high an AIF value to meet ABC requirements. The methodology outlined in ABC Division B Part 11 is based on Canadian Mortgage and Housing Corporation’s (CMHC’s) 1981 guide, New Housing and Airport Noise. It offers guidance on how to provide building envelope assemblies with higher noise
16
CONSTRUCTION CANADA ACOUSTICS
An artist rendering of the Telus Spark building, as seen from the south.
isolation properties for buildings located closer to airport runways. By following this strategy, rooms became usable for their required purpose, but that still does not mean aircraft noise will not be heard inside the science centre. The original proposed exterior assemblies were as follows: • Type 1 Roof––waterproof membrane, membrane underlay, 150-mm (5.9-in.) rigid insulation, air/vapour barrier membrane, gypsum sheathing, and metal deck; • Type 2 Roof––prefinished metal standing seam roof, 25-mm (1-in.) air space, 240-mm (9.4-in.) thermally broken nylon clip system, 150-mm rigid insulation, waterproof membrane, gypsum sheathing, and metal deck; • Type 1 Wall––prefinished insulated metal wall panels (i.e. bottom half of wall only), 152-mm (6-in.) metal studs, 13-mm (0.5-in.) plywood, and 16-mm (0.6-in.) gypsum board; • Type 2 Wall––aluminum curtain wall frame with sealed glass units (6-mm [0.2-in.] glass, 13-mm air space, and 6-mm glass), and insulated glass spandrel panels; and • Type 3 Wall––prefinished metal panel, panel support clip system and air space, 75-mm (3-in.) semi-rigid insulation and metal Z-bars, air/vapour barrier membrane, 13-mm exterior gypsum sheathing, 92-mm (3.6-in.) or 152-mm steel studs, and steel framing. The main gallery areas have suspended radiant cooling panels and suspended radiant heating panels along the exterior walls that do not provide additional noise isolation properties to the roof assembly. Some spaces, such as classrooms, have suspended T-bar ceiling systems with mineral fibre tiles. The classrooms have more windows and skylights than other areas of the building. There is also a raised section of the science centre over part of the central atrium and main stairway with clerestory windows. The windows are double-glazed insulating units with 6-mm glass, 13-mm air space, and 6-mm glass, mounted in thermally broken aluminum curtain wall type frames and are relatively lightweight. The initial aircraft analysis indicated upgrades were required to the originally proposed assemblies to meet minimum ABC requirements. The upgrades included a 125-mm (5-in.) thick concrete topping on the metal deck roof, and the addition of a metal stud and gypsum board layer for the top half of the walls. One of the window panes was upgraded from 6-mm glass to 6-mm laminated glass. These upgrades were sufficient to meet minimum ABC requirements, but did not necessarily meet the science centre’s needs regarding the audibility of aircraft noise within the building. A second type of aircraft noise analysis was also undertaken. The methodology ABC outlines does not provide an indication of how loud a single aircraft fly-over event
17
CONSTRUCTION CANADA ACOUSTICS
An artist rendering of the building, view from the southwest.
would be at the science centre site. To determine this, one-third octave band maximum sound pressure levels of aircraft flying overhead were gauged with a precision sound level meter. Both jet aircrafts and propeller aircrafts were measured; however, a smaller propeller aircraft turning onto final approach directly over the site was one of the loudest sound pressure levels measured. The measurements indicated there were significant levels of low frequency energy from the aircraft. The measured level ranged from 74 to 79 dBA and 79 to 87 dBC. (The dBA sound pressure level is filtered through the ‘A’ filtering network to approximate human hearing response. The dBC sound pressure level is filtered through the ‘C’ filtering network and has much less attenuation of the low frequency sounds.) Of particular concern was the science centre’s Dome Theatre, as this space had a very low background noise criteria (NC) design requirement. The target was a maximum NC of 25. This theatre has a dome screen with three-dimensional (3-D) video capability and high-quality surround sound. The originally proposed metal roof and wall system for this space would not have provided the required noise isolation properties, even with a 150-mm thick concrete topping. To obtain the required noise isolation, an inner resilient-mounted gypsum board ceiling and wall were required. The Dome Theatre has a sloping roof and walls; the solution for applying concrete to these walls was to use shotcrete––a spray-applied concrete.
Heavy rail, light rail, and freeway noise isolation To determine the noise impact to the site from heavy rail and freeway traffic, one-third octave band maximum sound pressure level measurements were undertaken at the site. As the LRT is not yet present at the site, sound pressure level measurements were undertaken of some existing light-rail pass-bys at a location beside an existing line in south Calgary. The engine pass-by sound levels of the diesel locomotive on the CP Rail line had significant low-frequency energy levels similar to the aircraft. The noise from freeway traffic heard at the site was generally lower than the aircraft and heavy rail noise; the loudest freeway noise events were from trucks and motorcycles. Therefore, the noise isolation required for the aircraft would provide sufficient noise isolation for the heavy rail and freeway noise. The LRT pass-by measurements also indicated high maximum noise levels because of the close proximity of the proposed right-of-way to the science centre.
18
CONSTRUCTION CANADA ACOUSTICS
View from the west on November 1, 2010, after the exterior wall installation is underway.
View from the west, before installation of the Dome Theatre’s exterior finish. Theatre-raked seating tiers are visible and traffic on Deerfoot Trail freeway can be seen in the distance.
The Presentation Theatre interior on June 28, 2011. The wall on the left is adjacent to the light rapid transit (LRT) right-of-way.
The science centre’s most critical room with regard to the future LRT line is the Presentation Theatre, located on the east side, directly adjacent to the proposed LRT right-of-way. The design target in this theatre was a maximum NC of 30. Calculations indicated three layers of 16-mm (0.6-in.) gypsum board on metal studs with acoustic insulation in the stud space would provide the required noise isolation. Based on the LRT sound level measurements, two layers of 16-mm gypsum board on metal studs were used for the upper gallery exterior walls, and one layer of gypsum board on top of a 13-mm (0.5-in.) plywood layer on metal studs for the lower portion of the gallery walls. This assembly provides the flexibility to construct classrooms along the science centre’s east exterior wall in the future and meet a maximum NC of 35.
19
CONSTRUCTION CANADA ACOUSTICS
This map shows the lands in the Calgary International Airport vicinity protection area and the noise exposure forecast (NEF) contour lines. Image courtesy Calgary AVPA Regulation 2009
The windows were also reviewed, and the windows and skylights in the classrooms required an upgrade to meet ABC and the target background NC levels. As the design progressed, the skylights were removed from the classrooms. With their elimination, and substituting a layer of laminated glass for one of the panes in the sealed doublepane window assemblies located in the classroom, the exterior walls met the ABC requirements. Further upgrades to the windows, such as laminating both panes and providing a larger air space were reviewed. As the most critical rooms—the Dome Theatre and the Presentation Theatre––did not have windows, it was decided further noise isolation upgrades to the windows for other less noise critical spaces would not be incorporated into the design. The exterior building envelope noise isolation measures incorporated into the building design ensure the sounds heard within the building are those of the various displays and programs rather than the noise from the surrounding planes, trains, and automobiles.
20
CONSTRUCTION CANADA ACOUSTICS
Part Three The Green Soundscape
BY NIKLAS MOELLER, MBA
Niklas Moeller, MBA, is vice-president of K.R. Moeller Associates (Burlington, Ont.), a global developer and manufacturer of soundmasking systems. He has been in the soundmasking business since 1998. Moeller can be reached via e-mail at nmoeller@ logison.com.
21
CONSTRUCTION CANADA ACOUSTICS
Photo © Janet Trost Photography
The Green Soundscape
Addressing acoustics in sustainable offices For many people, the term ‘green building’ simply means wasting minimal resources. However, to be successful, these facilities must also be environments where employees can thrive and productivity can soar. For this reason, a substantial number of the credits offered by Leadership in Energy and Environmental Design (LEED) are for factors affecting indoor environmental quality (IEQ).
22
CONSTRUCTION CANADA ACOUSTICS
An example of soundmasking’s effect on speech intelligibility. Images courtesy K.R. Moeller Associates
Acoustics are as important to IEQ––and to comfort and concentration––as light, temperature, and humidity. However, green buildings often perform poorly in this area. In fact, post occupancy evaluations conducted by the Center for the Built Environment (CBE) at the University of California, Berkeley, found occupants of green buildings are generally more dissatisfied with acoustics than those in traditional facilities.1 CBE’s surveys revealed the most common sources of irritation and distraction in green spaces are people talking around occupants, talking on phones, overhearing private conversations, and telephones ringing. Office equipment and outdoor noise are also concerns. When CBE asked respondents to evaluate their job performance in these noisy environments, 60 per cent declared noise inhibits their work. Others have also found acoustic problems in various green office building evaluations.2
Acoustic design goals To maximize comfort and productivity, the workplace should provide occupants with speech privacy and freedom from distracting noises, enabling them to concentrate and work without disrupting others. Many green buildings are not meeting these goals for several reasons. An explanation frequently cited is the fact LEED––arguably the best known green building rating system––only offers explicit acoustic credits for healthcare facilities and schools. Criteria have yet to be established for commercial interiors, perhaps leading this aspect of their design to be overlooked. Further, these buildings can achieve high LEED ratings by satisfying requirements that are actually detrimental to acoustics.
23
CONSTRUCTION CANADA ACOUSTICS
Absorptive materials reduce the noise volume, as well as the length of time sounds last and the distance they travel.
LEED credits are not always sought for green designs. Still, other sustainable structures often fail to achieve key acoustic goals. The reason seems to lie in the fact that many current sustainable design strategies unintentionally contravene the formula used to achieve effective acoustics. This is known as the ‘ABC Rule,’ which stands for absorb, block, and cover.
Absorb When a sound hits an absorptive material, its energy is reduced, decreasing its volume, the length of time it lasts, and the distance over which it travels. Unfortunately, the majority of green buildings use hard-surfaced materials at the expense of absorptive ones. These surfaces are highly reflective, causing sounds and conversations to echo, overlap, linger, and travel greater distances. The resulting environment is noisy, distracting, and tiring for occupants. Since the ceiling offers the largest unimpeded surface within most facilities, using absorption in this location is essential. However, many green buildings have open ceilings because they promote natural light penetration from the windows. It is also thought the exposed deck can be used as a heat sink to help control the temperature within the building. Further, eliminating the suspended ceiling reduces material costs. If an open ceiling is used because of a desire to implement passive heating/ cooling, it is important to ensure there will be enough concrete in the deck to succeed. There must be at least 203 mm (8 in.) to provide any meaningful thermal storage beyond what is lost through the building envelope. Unfortunately, many buildings do not meet this requirement. In this case, the suspended ceiling would be eliminated without cause. If cost is an issue, it is key to look beyond the initial savings. For example, the Ceilings and Interior Systems Construction Association (CISCA) found office spaces with a
24
CONSTRUCTION CANADA ACOUSTICS
Blocking can be achieved using workstations, while still accommodating the need for daylighting.
suspended ceiling cost between 15 and 20 per cent more up front, but show substantial savings over their life in terms of HVAC, due to the efficiency of the plenum. Lighting costs are also lower because the reflectance is better for ceilings than for concrete decks. CISCA showed overall energy savings to be between nine and 10.3 per cent. They also determined payback on ceilings never exceeds 1.6 years, and if the suspended ceiling is replaced by another type of absorption, then the return on investment (ROI) is even faster. Including a suspended ceiling in the building’s design is ideal. In open spaces, designers should use a tile with at least a 0.75 noise reduction coefficient (NRC). In closed spaces, they should consider a tile with a high ceiling attenuation class (CAC) because it will be better at containing sounds, decreasing what can be heard from office to office. If this route is not taken, absorption needs to be provided by other means. Simply adding absorptive panels to a portion of the deck (e.g. 30 per cent) will have an impact. Another alternative is to use vertical baffles. If a concrete deck is not necessary, but an open ceiling is still desired, another option is to use a perforated and corrugated metal deck with an absorptive material—such as fibreglass—placed behind the perforations before the concrete is poured. As they also present a large area, workstation partitions should be absorptive as well, particularly if there is no acoustical ceiling. If fully absorptive panels are too expensive, some furniture systems offer different surfacing on the interior and exterior of the partitions. Absorptive material should at least be used on the inside of the workstation, above the work surface, so the volume of the occupant’s voice is reduced before it is reflected back into the space. It is also important to implement soft flooring. If a hard floor is used, it will result in more footfall and ‘traffic’ noise, creating a noisier, less comfortable environment.
25
CONSTRUCTION CANADA ACOUSTICS
Covering noise with a soundmasking system also helps to support other sustainable design choices.
Since they account for a large percentage of the space, the materials selected for the ceiling, workstations, walls, and flooring can significantly contribute to a project’s sustainability goals. Acoustic materials are available that are renewable, reusable, recycled, or recyclable. When choosing materials, designers should also consider air quality factors such as off-gassing, volatile organic compound (VOC) content, and breathable fibre.
Block Another method of controlling noise is to block sound transmission. Barriers, such as walls, windows, doors, workstations, and other physical structures are typically used for this purpose. However, the drive to maximize daylighting and promote air circulation in green buildings often involves sacrificing many of this strategy’s key elements. For example, most green designs feature a higher percentage of open plan space than traditional buildings, as well as low workstation partitions (or, in some cases, none at all). These open spaces allow sounds to travel unimpeded over greater distances, contributing to overall noise levels. Open spaces also allow conversations to easily travel to unintended listeners. Furthermore, lowering or eliminating partitions decreases the amount of absorption they could have otherwise provided. When selecting workstations, height is essential. There is general agreement in the acoustical industry that workstation panels should be above seated head height, which is 1524 to 1651 mm (60 to 65 in.). If they are shorter, they achieve little more than holding up the desk. If daylighting is also a priority, the best compromise is to use absorptive panels up to a 1219-mm (48-in.) height and top them with 305 mm (12 in.) of glass or another transparent material, allowing light to pass through while physically blocking sound in
26
CONSTRUCTION CANADA ACOUSTICS
Hard surfaces are highly reflective, causing noises to echo and travel greater distances. Without consideration, this can be problematic. Photo Š Kristian Dahl. Photo courtesy iStockphoto.com
the local area. This solution is not ideal because the glass reflects sound, but it provides a balance between the lighting and acoustic requirements. Workstations should also block sound. The success with which they will do so is indicated by their sound transmission class (STC) rating. It is important to note whether the STC was tested in the lab or the real world, as the former are usually conducted in perfectly sealed conditions and may not represent performance in actual applications. Also, designers should verify the partitions are well sealed along any joints and there are no significant openings between or below the panels. In closed spaces, one must pay attention to any penetrations because they can become pathways for conversations and noise. For example, return air grilles, ductwork, or the plenum itself, can transmit sound. Green designs increasingly employ re-usable, demountable wall assemblies. While these reduce waste over their lifecycle, they may not provide the sound isolation level needed from one closed space to another (e.g. between offices and meeting rooms). Demountable systems may have lower STC ratings than a gypsum wall and the joints between panels may provide conduits for sound. Gaps along the ceiling, exterior walls, and the floor also easily transmit sound and should be addressed during installation. Many wall systems provide cable management raceways along the bottom. While the wall panels themselves may provide good sound-blocking performance, these raceways are often open space along the bottom, covered on each side by plastic or metal, which can easily transmit sound. A good septum dividing each side of the wall is advisable.
27
CONSTRUCTION CANADA ACOUSTICS
The desire for daylighting can also change the building’s overall shape. The narrower a facility is from the window to the core, the more easily natural light penetrates. However, narrow spaces also reflect more sound over distance, similar to the ‘bowling alley’ effect experienced in long corridors. Sounds ricochet between the exterior wall and the core. In traditional buildings, larger, squarer footplates are common, and exterior walls tend to be further apart. While it may not be possible to avoid narrower spaces if daylighting is essential, it is important to acknowledge the impact these narrow footprints have and ensure other steps are taken to compensate. For example, absorptive panels may need to be used at points throughout the long space to reduce reflection.
Cover Many people believe they have achieved good acoustics after applying the preceding strategies and the sound level in their facility is very low. Yet, just as with lighting and temperature, the comfort zone for the volume of background sound is actually not zero. If it is too low, conversations and noises are easily heard and more disruptive. Ensuring a comfortable and sufficient background sound level is the final requirement of the ABC rule, which is to cover up any conversation and noise remaining in the space. Due to using natural ventilation, the background sound level is often lower in green buildings than in traditional facilities, making it easier to hear conversations and noises from a distance. Further, if open windows are used to assist air circulation, exterior sounds easily travel into the space, disrupting occupants. Passive heating and cooling systems also reduce the ambient sound level. If different strategies are used along the exterior versus the building core, mechanical systems can yield variable acoustical conditions, contributing to overall acoustic problems. In any case, a mechanical airflow system could never be relied on to provide a consistent background sound level throughout the day because it turns on and off. In fact, these cycles can make it a source of irritation itself. When the system is on, the sound it produces is also not at an appropriate volume level or in the correct frequency spectrum to mask speech. Soundmasking systems provide the only way to truly replenish and keep the background sound level at an appropriate volume, which is typically between 42 and 48 decibels (dB). A soundmasking system consists of a series of loudspeakers, which are installed in a grid-like pattern in or above the ceiling. The system distributes a comfortable background sound, which most people compare to softly blowing air. This sound has been specifically engineered to increase speech privacy. It also improves general acoustical comfort by covering up many intermittent noises or reducing the amount of disruption they cause by decreasing the magnitude of change between baseline and peak volumes (i.e. dynamic range). In addition, if the soundmasking technology features small adjustment zones with fine control over volume and frequency, and it is installed throughout the space, it will also ensure acoustic consistency across the facility. Using a soundmasking system can help support sustainable design. For instance, natural ventilation can be used without the typical negative impact on privacy and noise levels. In an open space with few physical barriers, it will increase the external/
28
CONSTRUCTION CANADA ACOUSTICS
Providing occupants with speech privacy and freedom from distracting noises increases productivity and workplace satisfaction. Photo © Chris Schmidt. Photo courtesy iStockphoto.com
internal noise isolation, as well as the isolation between workplaces. Including masking systems can also help trim down material costs by, for example, reducing wall construction standards. Movable walls can also be used without compromising acoustics, offering buildings the potential to collect LEED points for construction waste and construction indoor air quality (IAQ). In this way, masking can also increase the space’s flexibility and reduce waste following renovations. There are a number of green attributes to consider when selecting a soundmasking system. These factors include: • energy consumption; • adherence to programs such as the Restriction of Hazardous Substances (RoHS); • lifecycle; and • the recycling program that the manufacturer offers for the end-of-life products.
Reduce noise at the source Recognizing a combination of all these methods is required to create truly comfortable acoustic conditions––the ‘ABC rule’ is often referred to as the ‘rule of threes.’ However, there is one tactic it overlooks, which involves identifying and subsequently reducing or eliminating unnecessary noise sources. Decreasing noise at the source can be achieved by implementing workplace rules and using quieter building and workplace equipment. This can be a very effective strategy, but only to a point. People will always generate noise as they go about accomplishing their tasks.
29
CONSTRUCTION CANADA ACOUSTICS
Soundmasking addresses speech privacy and noise issues by distributing a background sound throughout the workplace.
If a building fails acoustically, is it green? There is no doubt current green design practices pose a challenge to acoustics and, consequently, to workplace satisfaction and productivity. While addressing acoustics incurs some cost, this expenditure must be weighed against the long-term negative impact of poor noise control and speech privacy on comfort and performance. After all, employees account for between 80 and 90 per cent of an organization’s costs. Even a small impact on their productivity can easily outweigh any initial savings. In “Acoustic Design in Green Buildings,” Field asks, “whether a building that is not comfortable acoustically, and therefore not fit for its purpose, is actually a sustainable building for its occupants.”3 Indeed, it can be argued if a building fails to provide a healthy and fully functional environment, it might not be ‘green’ at all.
Notes 1
See S. Abbaszadeh, L. Zagreus, D. Lehrer, and C. Huizenga’s “Occupant Satisfaction With Indoor Environmental Quality in Green Buildings,” in Proceedings, Healthy Buildings, (Lisbon, Portugal, June 2006, [vol. 3, 365-370]), as well as J. Heerwagen and L. Zagreus’s “The Human Factors of Sustainability: A Post Occupancy Evaluation of the Philip Merrill Environmental Centre” Summary Report for the U.S. Department of Energy (DOE), Center for the Built Environment, University of California, Berkeley, California (April 2005). 2 See M. Hodgson’s “Acoustical Evaluation of Six ‘Green’ Office Buildings,” in the Journal of Green Building, (3[4], 108-118, 2008), as well as “Green Buildings: What’s Working, What’s Not,” which appeared in Building Design and Construction’s June 9, 2006 edition of eShow Daily. 3 See C. Field’s “Acoustic Design in Green Buildings,” in the ASHRAE Journal (50 [9], 60-70, 2008).
30
CONSTRUCTION CANADA ACOUSTICS
Part Four Studio Sound
BY OLIVER BARKOVIC, B.ENG.
Oliver Barkovic, B.Eng., is a graduate of McMaster University and the president of Forward Acoustics, a manufacturer of Canadian-made acoustic products. He can be reached at info@forwardacoustics.com.
31
CONSTRUCTION CANADA ACOUSTICS
Photos courtesy Forward Acoustics
Studio Sound Adapting acoustical techniques for commercial, office, and institutional spaces
George Martin, the Beatles’ renowned producer, once said, “A physicist will tell you that space is allied to time, but a record producer will argue that it is closely allied to sound as well.” Therefore, it is no surprise recording studios and radio/television broadcast studios are among the most demanding acoustic environments. They are precisely tuned to achieve the optimal acoustic effects, such as: • background noise elimination; • delivery of clear, crisp speech; • absence of echo; and • precise use of reverberation.
32
CONSTRUCTION CANADA ACOUSTICS
Whether a recording studio or a conference room, honeycomb-shaped acoustic ceiling clouds prevent reflection and control reverb in a space with high ceilings.
The results can give a studio a distinct personality, and sometimes even make it famous, attracting musicians from far and wide. Few are more elaborate than the famed Tower Records Studios in Hollywood, featuring 254-mm (10-in.) thick exterior concrete walls, separated from the interior walls by an air gap, as well as triple-layered flooring of rubber, cork, and concrete. Another studio, 9 m (30 ft) underground, the Capitol Records complex houses trapezoid-shaped echo chambers––designed by guitarist and songwriter Les Paul––that can support reverberation times of more than five seconds. In these spaces, recording engineers can precisely tailor their recordings to get the exact feeling they want for a song or album. Closer to home, the Beauty Industries music recording studio in Hamilton was designed with great acoustics in mind, and the acoustic details at work in this space can offer guidance for other common spaces. Triple-thick walls and underground bunkers do not appear on very many specification sheets, to say the least. However, some of the approaches used by the professionals in studio spaces can be adapted to improve the acoustic environments in a wide range of spaces where good communication is critical, such as boardrooms, offices, call centres, and videoconference facilities.
Making acoustics work The features that make acoustics work in studio spaces are the room’s shape and size, including high ceilings (if possible) and surface treatment where necessary.
Room shape Non-parallel walls are ideal for a recording studio space because reflections are randomized and the modal distribution is less uniform, producing several zones completely free of first-order reflections. In Les Paul’s underground bunkers, and in the
33
CONSTRUCTION CANADA ACOUSTICS
This radio station studio required a high proportion of absorptive treatment, using surface area on the walls and ceiling.
Beauty Industries studio, the rooms are a trapezoidal shape. This may be a tall order, especially in retrofit situations, so the next best guidance is that rooms should avoid 2:1 length-to-width ratios when possible.
Room size The bigger the room, the better. For example, the main studio at New York’s famous Hit Factory on West 54th Street spans more than 15 x 15 m (50 x 50 ft) with 9-m (30-ft) ceilings. Not only does this allow the space to accommodate a 60-piece orchestra, but it also benefits single musicians by reducing first-order reflections from nearby walls.
High ceilings High ceilings are better than lower ones––the greater distance from the ceiling to the usable space below gives sound more time to dissipate, reducing echo. In many studio spaces, the ceilings are more than 3.7 m (12 ft) high and are treated with suspended acoustic clouds.
Absorptive treatments In the Beauty Industries studio, a high proportion of the wall and ceiling surfaces have been treated. At the front of the space, the recording engineer is surrounded on three sides by floor-to-ceiling absorptive panels wrapped in a dark woven acoustic fabric, trimmed with acrylic for visual interest.
Lessons for offices and other spaces When building a recording studio, acoustics are top of mind; however, when building an office or institutional space, the auditory environment can often be an afterthought.
34
CONSTRUCTION CANADA ACOUSTICS
This recording studio features wall treatments that completely cover the surface area of the walls to reduce echo and reverberation.
This vocal booth has been treated to produce a precise acoustical environment, minimizing ambient noise and maximizing speech clarity.
What can be learned from these demanding acoustic environments when trying to improve the sound environment in office, commercial, or institutional buildings? Interior finishes chosen for esthetics or functionality can help or hinder acoustic performance. For example, in office spaces, smooth, reflective drywall is everywhere, but it is the enemy of good acoustics. Similarly, trends toward smaller, flexible spaces mean more walls, closer in, creating first-order reflections that bounce sound around workspaces, meeting spaces, and hallways. Open-plan offices are great for space efficiency, co-operative work, and effective supervision, but they raise perennial complaints among workers about lack of privacy and the inability to concentrate. Good acoustics can go a long way to creating a more comfortable, productive work environment. One should learn from recording studios that the effective isolation of instrumentation is key by noting who and what the noisemakers are in the space, keeping loud with loud and quiet with quiet. One should group loud spaces like photocopier areas, HVAC outlets,
35
CONSTRUCTION CANADA ACOUSTICS
Broadcast and recording studios are demanding auditory environments where engineers go to extraordinary lengths to achieve the right sound. Designers of offices and other spaces can employ some of their tricks of the trade to make everyday spaces sound great.
coffee stations, washrooms, and elevators together, while keeping quiet workspaces away from these background distractions.
Workstation dividers will not cut it Many offices use panelled workstation dividers. Therefore, is acoustic treatment still necessary? In many cases, the answer is yes––especially where the dividers are lower, allowing sound to travel over top. Also, in some cases, the dividers are not absorptive enough because they have not used specialized acoustic fabric, or have a non-absorptive core. Additional absorptive treatment on the walls and ceilings to achieve between 25 and 40 per cent coverage in each work area will work wonders. Many studios feature extra-high ceilings with suspended acoustic clouds, often hung by brackets or aircraft cable. Acoustic clouds are a great idea for office and institutional spaces as well, because they are much more acoustically effective than compressed cardboard ceiling tile. Where the suspension grid for compressed tile already exists, fabric-wrapped panels can be swapped in for an easy retrofit fix.
36
CONSTRUCTION CANADA ACOUSTICS
In Beauty Industries’ Hamilton sound recording studio, the front wall has been treated with floor-to-ceiling acoustic panelling.
Lessons for boardrooms While the office boardroom may be where an organization’s most important business is done, these spaces ironically often have some of the most acute acoustic challenges. Office workers wonder why it can be so difficult to hear someone clearly when they are just at the other end of the table. The typical boardroom is the antithesis of the acoustic ideal found in studio spaces. Relatively small spaces, smooth surfaces, low ceilings, HVAC, and ambient noise from computers and projectors can conspire to render some boardrooms virtual echo chambers. Many boardrooms also include a conference call unit placed in the centre of the table. Acoustically, this arrangement could not be worse, with the sound being directed straight up toward a reflective drywall ceiling––creating echo and reverb that makes hearing difficult for those in the room, and especially for those on the phone. In rooms with numerous windows, whiteboards, or other features, wall space can be scarce, so the ceiling is a good place to start when looking to increase the surface area that can be treated with absorptive panelling. On the walls, custom panels can be fit into irregular spaces to make the most of the wall space that does exist.
Videoconference facilities Companies and organizations are investing additional resources into videoconferencing to save on travel time and expenses and to allow more employees to telecommute.
37
CONSTRUCTION CANADA ACOUSTICS
As videoconferencing gains popularity, a boardroom’s acoustics become even more important. Photo Š iStockphoto/Bedo
However, meetings must look and sound professional, even if they are not in person. Virtual meetings where some participants cannot be heard or well-understood, or where participants sound like they are speaking into a bucket, are simply not satisfactory. Perhaps more than any other office space, videoconference suites are much like small recording studios in that external noise must be minimized and the interior space should be treated to maximize the crispness and intelligibility of speech, while reducing echo and distortion. Echo and reverberation can also distort the audio signal. This issue can be overcome by incorporating more expensive echo-cancellation functionality in the videoconference hardware. However, that step may not be necessary in a space designed for optimal acoustics. Videoconference facilities are often located in small rooms where space is at a premium. One should consider the acoustical impact of everything in the space, including countering the reflective effect of smooth-topped tables and windows or other surfaces. If possible, it may help to minimize the use of glass-fronted art or whiteboards that introduce additional reflections.
38
CONSTRUCTION CANADA ACOUSTICS
Ceiling-mounted panels of varying depths provide broad-spectrum sound absorption and diffusion. Photo courtesy Forward Acoustics
Choosing acoustic treatments One should make the most of the surface area available for acoustic treatment by opting for high-density absorption. Fabric-wrapped panels with a fibreglass insulation core are a good choice as the interior insulation is far denser than other alternatives like foam, and less square footage is required to achieve the same acoustic effect. One should look for fabric-wrapped panels with a wood frame as they are more durable than resin-hardened panels and introduce an air gap between the insulation and covering fabric that enhances acoustical performance. For offices and institutional settings, perforated or slatted wood-veneer panels with an absorptive core are another good choice for their durability and esthetics. They have the same absorptive core as a fabric-wrapped panel, with an additional sound-diffusive veneer that can be customized in order to co-ordinate with the other millwork in an office or institutional interior.
Tips for architects, designers, and specifiers One should consider the following principles when seeking to improve the acoustics in commercial and institutional spaces.
Loud with loud, quiet with quiet At the design stage, one should try to group noisy activities together and away from quiet workspaces. This will save headaches and expense down the road.
39
CONSTRUCTION CANADA ACOUSTICS
Radio broadcast studios minimize reflections with wall-mounted absorptive panels. Photo © iStockphoto/M Morgan Photography
Plan for acoustics before occupancy One should consider the space’s sound-related needs and include acoustics as early in the workplan as possible. Acoustic panelling should be installed in advance of, or in conjunction with, interior furnishings and workstations. Once occupancy takes place, one should check back with occupants for problem areas that may require additional treatment.
Make use of every surface Artwork and other interior fittings need not limit the surface area available for acoustic treatment. Using custom fabric-wrapped or wood-veneer acoustic panelling, it is possible to hang artwork and signage on top of acoustic treatments. It is not necessary to treat the entire surface the way one sometimes sees it in recording studios, but a distribution of acoustic absorption within the space––to a coverage of approximately 25 to 40 per cent––is ideal. One should also remember to make the most of the surface area available by choosing acoustic treatments that offer high-density absorption.
Remember the little spaces Boardrooms, videoconference rooms, lunchrooms, and other small to medium-sized spaces can suffer the most from common acoustic issues. One should make sure to treat these spaces as well as the wide-open office areas.
Conclusion Professional studio spaces are highly specialized acoustic environments with very individualized needs. However, there are lessons to be learned for everyday commercial and institutional spaces that can improve the acoustical functioning for those who visit them, or those who work in them.
40
CONSTRUCTION CANADA ACOUSTICS
Part Five Sound Attenuation for Piping Systems
BY TIM MEADOWS
Tim Meadows is vice-president of sales for Victaulic in Canada, and has 22 years of industry and pipe joining expertise. He is actively involved in various industry associations, including the Canadian Institute of Plumbing and Heating (CIPH) and the Mechanical Contractors Association of Canada (MCAC), where he is the executive committee’s associate council chairman. Meadows can be reached via e-mail at tmeadows@victaulic.com.
41
CONSTRUCTION CANADA ACOUSTICS
Images courtesy Victaulic
Sound Attenuation for
Piping Systems Noise carried through piping systems has become a more significant challenge to specifiers, architects, engineers, contractors, and owners. Today, changing design requirements place mechanical rooms on intermediate and top-floor building levels, and greater use of lightweight construction materials tend to vibrate more than traditional heavy ones.
42
CONSTRUCTION CANADA ACOUSTICS
In a mechanical room, using flexible couplings at connections on the pumps attains a level of vibration attenuation to improve the acoustics of the piping system.
It is not surprising a sizable industry has grown around the idea of minimizing pipingborne noise. If systems that serve to attenuate sound are not specified at the design stage, noise issues can continue to be a problem throughout the structure’s lifecycle. This can result in unsatisfied owners whose occupants complain about noise that is distracting enough to affect concentration and productivity. In this way, sound-control issues can also have a bottom-line impact on the engineer or contractor, who may need to perform numerous callbacks in an attempt to fix the problem. The surest way to avoid the issue is to bring an acoustics professional into the project at the design stage. However, budgets do not always permit this, and there are many construction-grade projects where the owner does not consider sound to be a critical compound, at least until after the fact. This article focuses on the proven sound attenuation benefits of a technique commonly thought of as a productivity-enhancing tool––the grooved mechanical pipe joint. Most often specified when contractors are seeking a fast, easy, safe, and reliable alternative to welding, grooved mechanical pipe joining has a long history of effectively minimizing noise and vibration in applications around the globe.
Traditional sound attenuation methods When faced with the need to diminish noise and vibration from equipment connected to the circulation system, designers have traditionally specified elastomeric flexible arch connectors. These create a discontinuity in the metal piping (as opposed to welding), so less vibration is transferred down the line. Additionally, they are commonly constructed of nylon, polyethelene terephthalate (PET or PETE), or polyester material to help absorb vibration, and are formed in a spheroidal shape to permit deflection in all directions.
43
CONSTRUCTION CANADA ACOUSTICS
This shows the percentage of additional decrease in sound provided by three grooved mechanical couplings. Independent testing showed that couplings provide a significant reduction in sound vibration.
This advantage is also the elastomeric arch’s weakness. As the elastomeric flex connector’s shape allows pressure to exert in all directions, control units such as restraining rods, plates, and/or anchors are required. These are used to prevent excessive stretching of the unsupported elastomer due to system pressure thrusts. Yet, when such thrusts repeatedly occur, and the connector is overextended through time, use, and pressure, failure can result. Flex connectors also employ unrestrained rubber as a pressure boundary in systems that otherwise have continuous metallic encasement. This becomes a particular concern in high-rise construction where large pressure differentials are often present. The reinforcing systems’ complexity also means installation can be time-consuming, and post-commissioning adjustments may be required. As a result, such connectors are usually placed only at the point where the pump or other equipment connects directly to the piping.
The grooved solution To find alternative solutions, independent tests were performed by Nutech Testing Corporation/SE Laboratories (San Jose, Calif.)––a laboratory specializing in environmental and field mechanical testing. During this research, another method was found to be at least as effective in sound attenuation as flexible arch connectors.
44
CONSTRUCTION CANADA ACOUSTICS
In Vancouver’s tallest building, the luxury hotel and residence Shangri-La, grooved piping and flexible couplings were used to provide noise and vibration control in the mechanical systems, ensuring an optimal living environment.
Interestingly enough, this ‘new’ solution was invented more than 90 years ago, and has a major presence in the construction industry as a means for simplifying pipe joining, ensuring reliable connections, and shortening production schedules. This method was grooved mechanical pipe joining.
Inherent sound attenuation qualities When the grooved pipe coupling’s structure is examined, it is easy to see why it effectively reduces sound transmission. The resilient elastomeric gasket––contained inside the ductile iron housing’s internal cavity––creates a discontinuity similar to that of a flex connector. The material from which the gasket is made also serves to absorb vibration. The key distinctions of a grooved pipe joint over a flex connector are inherent in the coupling’s proprietary design. Its unique construction enables the gasket to seal against
45
CONSTRUCTION CANADA ACOUSTICS
The piping systems throughout the 511-m (1676-ft) Taipei 101 (Taiwan) must be able to withstand the high pressures that come with being one of the world’s tallest towers.
the pipe, while the ductile iron housing provides both space for the elastomeric material to flex and containment to prevent overstretching. Overall, the coupling works to create a permanent leak-tight seal without need for additional reinforcement. Additionally, ductile iron has vibration-dampening qualities of its own, so the external housing also serves to absorb sound. The sound attenuation characteristics of grooved mechanical couplings are not a newly discovered phenomenon. Testing conducted by L.S. Goodfriend and Associates (Whippany, N.J.) in 1970–1971 concluded that grooved couplings reduce decibel (dB) levels from 2.3 to 12.1 over a wide frequency range. More recently, SSA Acoustics (Seattle, Wash.) conducted field measurements at their client’s request that showed three couplings placed in series in a pipe section have a superior performance to braided metal hoses as they dampened the overall vibration amplitude by 80 to 90 per cent. Yet, they have a comparable performance to twinsphere neoprene connectors. As the sound attenuation outcome of this arrangement depends only on the three couplings being placed near each other in close proximity to the vibration source, there are still numerous opportunities for design flexibility. In this way, grooved mechanical
46
CONSTRUCTION CANADA ACOUSTICS
In Taiwan’s Taipei Financial Center, grooved piping was used in the HVAC, plumbing, and fire protection systems to enable the system to flex with motion caused by seismic and wind forces, thus ensuring a safe and sound system.
pipe joints can deliver unsurpassed vibration isolation and sound attenuation characteristics, while still allowing owners, engineers, and contractors to achieve their vision.
Seismic protection lessons The sound attenuation characteristics of mechanical pipe joining are directly related to the coupling’s seismic benefits. Employed around the world in earthquake zones for their ability to absorb seismic stress, grooved mechanical pipe joints provide the flexing qualities needed in structures subject to movement. For example, Taiwan’s Taipei 101––currently the world’s sixth tallest tower at a height of 511 m (1676 ft)––is located in the Pacific Rim seismic zone. Its piping systems must be able to withstand not only high pressures, but also the building’s motion caused by seismic and wind forces. To maximize safety, the facility’s mechanical systems team selected grooved mechanical pipe joining for its HVAC, plumbing, and fire protection systems. This was due both to the mechanical pipe joints’ unique ability to enable a system to flex with seismic vibration without breaking apart, and to the productivity benefits of the coupling’s simple-to-install design. The same qualities that all mechanical pipe joining systems possess to accommodate seismic movements are what enable them to diminish vibration and noise. For example, seismic waves are characterized by a very high amplitude and very low frequency. As the frequency increases, the resulting vibration starts to resonate, producing noise. By diminishing the transference of vibration, mechanical couplings reduce sound.
Cumulative sound attenuation Another benefit of mechanical coupling is each successive joint creates a further reduction in vibration. Builders of such sound-critical applications as the Alexandria
47
CONSTRUCTION CANADA ACOUSTICS
There are three possible ways to arrange grooved mechanical couplings in a piping system to deliver proven and effective vibration/sound attenuation.
Library in Egypt, the Esplanade theatre in Singapore, the Vancouver Convention Centre and Shangri-La hotel in Vancouver, and the Winspear Centre in Edmonton have used mechanical joining throughout their HVAC and fire protection systems to take advantage of this feature. The net effect can be viewed in this way: continuous welded pipe is taken to be the factor of one (all vibration is transferred without interruption). Then, one grooved coupling (and elastomeric gasket) reduces noise transference and the ductile housing absorbs an additional amount of noise. That lowered vibration is then reduced by the same factor at the next joint. The same effect occurs again at each subsequent joint where a mechanical coupling is installed, providing a cumulative reduction in sound. The findings of the Nutech Testing Corporation/SE Laboratories research—which used mechanical couplings in its testing—concluded: For any given pipe diameter, vibration isolation increases as the number of couplings increases (i.e. less vibration is transmitted with each additional coupling) regardless of whether flexible or rigid couplings are used.
48
CONSTRUCTION CANADA ACOUSTICS
The flexibility of grooved-pipe couplings reduces the transmission of stresses through a piping system, while the gasket and ductile iron housing combine to dampen vibration.
This cumulative effect results in such significant attenuation of piping-borne sounds that builders using mechanical joining have successfully installed equipment rooms in areas previously never considered possible. For example, in the elegant Esplanade theatre in Singapore, the equipment room is located next to the theatre hall. In the innovative Swiss Re office tower in London, England, the pumping systems are placed on mid-level floors to provide greater energy efficiency. The sound attenuation qualities of mechanical joining contributed a great deal to these designs being realized and constructed. In any application where undesired noise is being transferred through the piping system, owners and engineers who specify mechanical joining receive two vitally important benefits—that is significantly higher productivity combined with significantly reduced sound. This provides both economic and quality advantages to all involved.
49
CONSTRUCTION CANADA ACOUSTICS
Photo courtesy Winspear Centre
Winspear Centre
Images courtesy Victaulic
Edmonton’s Winspear Centre is thought of as one of the world’s most acoustically sound concert halls, and has been referred to as the quietest building on the planet.
Grooved mechanical piping, as well as isolation of the system on springs, reduces noise and vibration within the system and provides maximum acoustic quality. Opened in 1997 in Edmonton, Winspear is one of the world’s most acoustically sound concert halls and home to the Edmonton Symphony Orchestra. It has been referred to as the quietest building in the world, and was designed to offer breathtaking features in an atmosphere of zero noise. Winspear required a piping system that would provide maximum acoustic quality. By using grooved piping in the pump, chiller, and boiler piping systems, designers achieved this. Three consecutive flexible couplings create the noise-dampening qualities of the system, while the elastomeric gaskets further reduce noise and vibration.
50
CONSTRUCTION CANADA ACOUSTICS
Shangri-La
As a landmark 62-floor five-star hotel and residence in downtown Vancouver, Shangri-La offers views of the water, cityscape, and North Shore mountains. Completed last year, the hotel is the city’s tallest building. To ensure an optimal living experience for guests and residents, grooved piping systems were used throughout the building. On the lower level and 44th floor mechanical rooms, using three flexible couplings connected to the pumps provided the noise and vibration control required without needing specialized and expensive metal flex connectors or rubber bellows.
51
CONSTRUCTION CANADA ACOUSTICS
Forget going back to the drawing board Septe ptem mber mbe ber 2014 4 Vol. Vol oll 56 No. ol. N 6
Desiig gn gniin ing g
Bay NE W CO Thundeer Ba URTHOU y’’ss SE
Ben Be enefi efi efit fits ts off car ca arb bon-c bon -cu cure red con Knowin Kn co onc cre cre wiing ret ete te g yo Wood-ffram your BIM BIM exe fra ram r ed fl ex xe ecuttio floo oor oors: tion ion pla rs s: s: Goiing p n ng n furt furt rth her h than the code 7 Vol. 56 No.
014_Cove
r.indd 1
October
magazine
of Construct ion Specifi ficcations t Canada
www.cons onstruct
2014
Surrey Designing Hospital’s Memorial
ioncanada
.net $7.95
CEL
CC_Sept2
AT EBR I
years
of
C
The offi ficial
NG
READ
C SC - D C
es’ Wood ‘Tre
es pes pe ipes p pi pip ed pipe bed bb b abbe ab abb hab h eh re re reh es es & reha re res ure xtture xt xtu err fixtur ttte s ettte ett es Bett che che rch s:: Be s arc arch es de ry ar rade ra nry grad onry on pg so g upg ing al mas b bing tal nta ntal mb ent lum Plum P ume onum Mon Mo fs ofs oof ro e flat roo ble ab kab alka wal g wal fing ofin rproofi erpr e atte ate Wat W
INSTEAD
December 2014 Vol. 56 No. 8
www.const ficial The offi
Randi Segal-Flanagan, ext. 218 Kris Nelson, ext. 230 Will Ellis, ext. 261
fications n Specifi of Constructio
ett ne a..ne da da.ne ad na an ncana onca ructio ructi 95 95 7..9 7. $7.95 $7 $
Canada 10/3/14
2:11 PM
Montréal University Hospital’s Research Centre
An increasing number of Architects, Engineers, and Specification Writers are turning to Construction Canada for the latest information and insight on the products and practices shaping the Canadian construction industry.
To place your ad call 800-409-8688:
magazine
Designing
Glazing and life safety Insulation innovations for buildings Contract admin for acoustics
The official magazine of Construction
Specifications Canada
www.constructioncanada.net $7.95
sales@constructioncanada.net Published by Kenilworth Publishing Inc. 15 Wertheim Court, #710, Richmond Hill, ON, L4B 3H7 Tel: 800-409-8688 Fax: 905-771-7336 www.constructioncanada.net