Achieving Acoustic Comfort in the Contemporary Office, Study notes of Microwave Engineering and Acoustics

Download Achieving Acoustic Comfort in the Contemporary Office and more Study notes Microwave Engineering and Acoustics in PDF only on Docsity! Sound MatterS How to achieve acoustic comfort in the contemporary office Produced by GSA Public Buildings Service December 2011 Part 1 What Is acoustical Comfort?........................................................................................... 4 Why Is It So Important? .................................................................................................... 4 How to deliver It? ............................................................................................................. 4 the Current Situation – What research is telling us...................................................... 6 the Challenge – Why acoustics is More Important than ever........................................ 9 the Solution – Checklist for Success ............................................................................ 10 Part 2 a Closer Look at the Where and How of acoustic Mitigation ....................................... 12 WHat: Behavior Works– the Human element of acoustics ........................................ 13 WHere: Zoning and designing Workplace neighborhoods ......................................... 18 HoW: technical tips for Physical acoustic Mitigation................................................. 28 Special Conditions & new acoustical treatments ........................................................ 37 talk Like an acoustician (or at least understand them) – a Short Glossary ............... 38 Putting it all together: Costs .......................................................................................... 40 references ........................................................................................................................41 acknowledgements ......................................................................................................... 42 This publication is dedicated to the unknown worker who, in response to a New York Times article, Beyond the Cubicle, by Allison Arieff, July 18, 2011, wrote the following internet comment: “I currently work in a cubicle – my neighbors are a man in the midst of a divorce, a woman with a problem child, another woman with an elderly parent who should be in a care facility. The only cure for my personal hell would be a quiet room with a door. Perhaps my employer would then get his money’s worth from my workday… did I mention that I am across from the copier?” This publication aims to show that there is a way out of this worker’s “personal hell”… but without a room, and without a door. As the Federal Government transitions to greater density and less private enclosure for economic and organizational reasons, acoustic performance will need to transition from a “side issue” to a “core issue.” January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 2 WHat IS aCouStICaL CoMfort? fiG 1. tranSlatinG Sound level into GraphicS loud Quiet a b c d Workplace distractions (letters refer to plan above) A. Conference room/teleconference.* B. Hallway discussion near workstations C Informal meetings and conversations D. Employees on the phone (especially standing above the acoustic absorption of the workstation or on a speakerphone) *This high level of noise is to be expected in a meeting area, but it may be a distraction to those outside the room who are uninvolved in the meeting itself. improved acoustic features 1. Low workstation partitions but with adequate seated privacy and acoustic absorption of NRC 0.7 in partition material located in front of the worker when seated, typically in any furniture partition. 2. High noise reduction coefficient (NRC) in the ceiling and/or on walls 3. A sound masking system 4. Enhanced employee awareness of co-workers Sound Matters will demonstrate how uncontrollable distractions (shown as red on the left) can be mitigated– rendering greater acoustical comfort–as shown in the same workplace with more quiet (blue) on the right. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 5 tHe Current SItuatIon—What the research Is telling us At the present time, work environments are doing a poor fiG 2. percent SatiSfied With environmental conditionS job of providing acoustical comfort. Results from GSA’s new old workplace research show that acoustic problems are a leading source of employee dissatisfaction in offices. amount of light Fig. 2 at right shows the pre- and post- results from seven federal offices that were redesigned to better visual comfort align with each agency’s business goals and missions. All of the projects emphasized improved communication Workspace Satisfaction and collaboration as a means to achieve the agency’s business goals. To support these goals, the physical daylight environment in each of the projects shared a cluster of views factors: lower workstation partitions to enhance visibility of work and people as well as to achieve LEED credits. building Satisfaction They also include spaces for spontaneous meetings, more varied meeting rooms, and more social spaces. noise levels In some instances, the projects incorporated small enclosed rooms for privacy and concentration. air Quality As can be seen in Fig. 2, there were substantial temperature improvements in almost all environmental factors except noise and voice privacy. The percent satisfied with Speech privacy noise and privacy was even lower than for temperature conditions, which are notoriously dissatisfying. Similar 0 20 40 60 80 100 results have been found in research on workplaces in the private sector.1 It should be noted that satisfaction with acoustics was low even before the renovations. Acoustic conditions have been a concern since the adoption of the open plan office decades ago. Myth: Reality: High cubicle partitions mean less noise, more privacy, Not true. Research shows that higher cubicle and fewer distractions. partitions block standing line of sight but provide small amounts of additional acoustical shielding. But this increase in ‘visual privacy’ may encourage people to talk louder because they think they have more privacy. Unfortunately, there may be less privacy and more disruption. 1 Heerwagen,J., K. Kampschroer, K. Powell, and L. Loftness, 2004. Collaborative Knowledge Work Environments. Building Research & Information. 32(6): 510-528. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 6 fiG 3. averaGe acouStic SatiSfaction S noise level Speech privacy core, by office type 3 Results from a large (approximately) 24,000 io n S co re 2 p<0.01 p<0.01 0.94 1 0.55 0.50 p<0.01 worker survey which shows that there is no statistical difference between worker satisfaction in high or low 0 p<0.01 p<0.01 -0.04 cubicle partition situations. In fact, no partitions scores -0.54 -0.31 -0.42 better. Enclosed offices are e S at is fa ct A ve ra g -1 -2 -3 Private Office Shared Office -1.57 High Partition Cubicle -1.27 -1.51 Low Partition Open Cubicle Office good, but are only .55 on a scale out of a possible+3 for speech privacy. Finally, the graphic shows much greater dissatisfaction with speech privacy than with noise intrusion. tHe Current SItuatIon—What the research Is telling us planninG: common miSconception veteran’S adminiStration Service center, reno, nevada The real noise problems are people having conversations with colleagues on the phone, in their workstations or in adjacent circulation areas. Because it is easier to see colleagues in a more open workplace, this generates more spontaneous conversation and more distractions for others doing quiet work. Both behavioral observations and survey results document this finding. Behavioral observations of a renovated GSA building in Philadelphia show that the number of interactions in workstations doubled in the new workspace due to the increased visibility of work.2 In a baseline survey for the GSA WorkPlace 20•20 program (which provided research and pilot feedback that the Center for Workplace Strategy follows), slightly more than 60% of the 3700 respondents said they often stop and talk to colleagues in workstations or in nearby corridors and 60% said they get useful information by overhearing conversations. At the same time, the majority of respondents complained about the noise which they contributed to generating: • 60% said they could get more done if it were quieter • 56% said the ability to insulate themselves from distractions was very important • 50% said noise keeps them from being as productive as they could be 2 Rashid, M., K. Kampschroer, J. Wineman, and C. Zimring, 2004. Face-to-face Interaction in Office Settings: What You Know About it May Not be Always True. Technical Report, Georgia Institute of Technology, College of Architecture, Atlanta, GA. This is one of seven workplace relocation projects whose results were studied and reported in Fig. 2. before after January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 7 tHe SoLutIon(S)—Checklist for Success The Facility Standard for the Public Building Service (PBS P-100) gives very usable technical specifications for acoustic mitigation methods, and nothing in Sound Matters should be seen as contradicting it. But the existence of obvious dissatisfaction with acoustics illustrated by Fig. 2 shows that P-100 criteria may not always be applied in practice, leading to spaces that do not perform as intended. To be optimally effective and affordable, integrated acoustic design requires that acoustics be considered at the beginning of the design process – not “fixed” afterward. Sound Matters describes ways to ensure that office workers will have the privacy and acoustical comfort they need to be effective. It summarizes solutions developed during an intensive two-day workshop sponsored by the PBS Center for Workspace. an acoustic charette was convened at the national institute of building Sciences (nibS) to provide guidance to pbS. The workshop included leading technical experts, industry representatives, behavioral scientists, and federal GSA-client agency representatives. There are three key areas of equal importance which need to be addressed to create acoustic comfort: • Behavior • Design • Acoustic Treatment Consistently integrating all three areas will deliver a workplace that is comfortable, sustainable and supportive of both interactive and quiet work. Even though good acoustics is a key contributor to interior quality - along with lighting, thermal conditions, ergonomics, and air quality – it is often an after-thought rather than an integral component of the contemporary workplace. Acoustic quality is even more critical today with aggressive federal goals to eliminate unused space4 and to achieve sustainability goals5 in new and renovated buildings. Reduction in space will lead to more intensely used workspace which may exacerbate current acoustic problems. In addition, sustainable design requires attention to materials used in furnishings and construction. Materials that achieve sustainability goals may not be the best choice for acoustic comfort. Goals to decrease energy use by enhancing daylight penetration can also inadvertently create acoustic problems associated with lower workstation panels which offer fewer opportunities for sound absorption. Concurrently, it has also been observed that the greater visibility of lower workstation panels increases the consideration of fellow workers when the occupant is aware of others in the space. Seated visual privacy strategies in smaller workstations with correspondingly larger or more frequent conference and support spaces can be more easily accepted when workers and their representatives realize how ineffective distance is at mitigating sound and how the greater visual separation from co-workers privacy of traditional workstations may make speech privacy far worse. The basic scientific principles of acoustics have been known for some time, and for particularly difficult situations such as auditoria and restaurants, the services of acousticians are regularly enlisted. This is not always the case with GSA projects, however. 4 Presidential memorandum on the disposal of unneeded federal space , June 10, 2010 5 Executive Order 13514 January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 10 tHe SoLutIon(S)—Checklist for Success Although acoustics has long been recognized as a critical component of sustainable design, acoustic expertise is generally missing from the discussion. The best way to mitigate contradictory goals to achieve a good solution is to integrate multi-disciplinary expertise from the beginning. Sound Matters is intended to change the current situation by putting acoustics on the table from the beginning of the project using the practical knowledge embedded in these guidelines. Sound Matters provides design teams with acoustic know- how that can be readily integrated into office planning. For most GSA work places, acoustic performance will be remarkably enhanced by attending to the guidance in Sound Matters. This document provides details and examples of how to improve acoustical comfort in today’s office. to increase the likelihood of acoustical design success and to avoid the need for expensive retrofits, the advice on the following pages should be considered by GSa personnel, architects, user groups, and others involved in the project. furthermore, in scopes of work, it is recommended that Sound matters be referenced with the requirement that designers “check off” items in ten StepS to conSider in achievinG acouStic comfort in the contemporary office, thus ensuring that they are a factor in the final design. ten StepS to achievinG acouStic comfort in the contemporary office BeHaVIor 1. Work patterns – Identify the balance of concentration and 2. Speech Privacy – Identify the level of privacy required for the 4. Behavioral protocols – develop protocols with the participation interaction among the workers work based on the work patterns of the subject work group, aimed in the office to help create zones. in the WSL. at reducing distractions and ’Reference PBS s Workplace Solutions Library (WSL) which has a survey to determine this. 3. Behavioral change – support behavioral adaptations with mobile technologies, multiple work appropriate use of space use. spaces, and policy. deSIGn 5. Zoning – After determining the work patterns, (see #1 above, 6. Planning – Carefully consider the effect on neighboring workstations natural light and view while allowing occupants to be aware of ”under “Behavior ), develop a when locating supporting activities other nearby workers. Where a work layout strategy which will locate such as copier rooms, coffee station partition is in front of the incompatible functions apart from bars and entries to conference worker when seated at the desk, the each other. Locate conference rooms where a queue could be noise reduction coefficient (NRC) and focus rooms convenient for anticipated – adjacent to large of the partition should be .07 so that ” interactive workers to “duck into conference rooms, for instance. speech is not reflected backward and to act as barriers between various work patterns. Consider elements such as file banks to further separate incompatible functions. 7. furniture – Select furniture which complies with LEED NC credits EQ 8.1 and 8.2 to obtain 1 or 2 LEED credits. The low partitions required will achieve the desired access to when the worker seated at his or her desk speaks. Where possible, the layout should locate the desks so that workers will not be speaking directly “at” each other. aCouStIC treatMent 8. Sound absorbing Ceilings and Walls – Specify ceilings having 9. Sound Masking Systems – Specify sound masking systems, 10. Walls – Specify Sound Rated Wall Constructions as follows: a minimum NRC of 0.9 in open particularly in open plan office >STC 53 minimum to isolate video plan office areas and NRC 0.8 areas. See page 42 for information conference and training rooms. in meeting rooms and training regarding sound masking systems. >STC 45 minimum to separate facilities. In conference, meeting conference rooms and and training facilities, provide executive office areas requiring absorptive panels on 25% of walls confidential speech privacy. with a minimum NRC of 0.8. >STC 40 minimum to separate private offices required in normal speech privacy. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 11 PART 2 A Closer Look at the What, Where and How of Acoustic Mitigation A systems approach is useful to integrate planning, design, specification, and construction of acoustical conditions. The decision framework described in this section is organized around simple steps in the following three areas: What WHAT behaviors are appropriate, based on work pattern analysis and knowledge of the impacts of acoustic discomfort on work performance. Where WHERE to house groups with different work patterns: zoning and designing workplace “neighborhoods” based upon how much workers need to concentrate or how much they need to communicate to get their work done. hoW HOW to apply acoustical treatments, including ways to block, absorb and cover disruptive sound. We may not be able to achieve ideal acoustics, but we can significantly improve them with the practical wisdom discussed in this section of the document. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 12 WHat: BeHaVIor WorkS–the Human element of acoustics Why should we care so much about distractions? Distractions are not just a source of annoyance and acoustic dissatisfaction. Distractions and interruptions also make it more difficult to do work. Specifically, research shows that distractions result in: • Shifts in attention that reduce focus; • increased efforts to concentrate, which can increase stress levels and fatigue; • Abandoning a current task to deal with demands caused by an interruption; • Losing flow of thought and the need to re-orient to the task, which can take up to 15 minutes. Research also shows that distractions and interruptions are most detrimental for complex cognitive tasks with high information processing demands.8 the 1980’s “cubicle” lives on as a fictitious room – and conveys fictitious privacy. Because the visual cues say “room,” occupants behave as though they are in a private room and tend to speak accordingly – sound goes right over the partition – easily distracting neighbors. Myth: Speech privacy means “I can’t hear you talking” or “I can’t see you when you’re talking.” Reality: Not true. Speech privacy is defined as “Techniques… to render speech unintelligible to casual listeners.” This definition is the foundation of enforcement procedures used for speech privacy under privacy laws such as those in the Health Insurance Portability and Accountability Act (HIPAA). 8 S.Lahlou, 1999. “Observing Cognitive Work in Offices.” In N.S. Streitz, J. Siegel, V. Hartkoff, and S. Konomi (Eds). Cooperative Buildings: Integrating Information, Organizations and Architecture. 2nd International Workshop, CoBuild ’99, Pittsburgh. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 15 WHat: BeHaVIor WorkS–the Human element of acoustics the need for Speech privacy Although the need for speech privacy is intermittent, the setting needs to provide acoustical conditions that support various degrees of speech privacy. As defined in Part 1, speech privacy refers to a condition in which people cannot fully hear or understand the words spoken by others located nearby. Several levels of speech privacy are defined in the ASTM standards: • Normal Privacy –This term means that some percentage of anything that is said may be understood by a casual listener. There are many types of information that are either less sensitive or require hearing the whole conversation to understand it. This is normal privacy: you cannot understand the whole conversation. Normal privacy is the baseline for achieving acoustical comfort in most “open” offices. • Confidential Privacy – Some information is wholly confidential. This term means that about 2% of anything that is said may be understood, but that the meaning of conversation cannot be determined by a casual listener. It is extremely difficult to achieve this level of privacy in an “open-landscape” office. Therefore, it is essential to design enclosed rooms that use the design strategies in Part 3: Detailed Acoustical Treatments. • Secure Privacy – This term means that 0% of anything that is said can be heard or understood by an unaided listener. This is the most difficult and expensive level of speech privacy to achieve. Because of its specialized applications, it is not covered in these guidelines. These levels can be related to ranges of the privacy index (PI) representing each level of speech privacy. Understanding 2 out of 10 words will render normal speech privacy, understanding 5 out of 100 words will render confidential speech privacy. to hear and be heard Although much attention is paid to voice privacy and reducing office distractions, speech intelligibility (being able to understand what is said) is also an important workplace goal even though it is far less of a problem in open office space than speech distractions. Plan to enable speech intelligibility where it is required most, for team meetings in small conference rooms to all- hands meetings or huddles in shared open spaces and, most typically, in formal conference rooms. Attending to speech intelligibility will also address the needs of the hearing impaired. Appropriate design needs to take into consideration room configuration, and selection of surface materials, including ceiling, wall, flooring and window treatments. The amount and placement of absorptive and reflective finish is discussed in detail in Part 3. Achieving speech intelligibility may require speakers and microphones that clarify and amplify rather than block or cover (mask) sound. Consequently, it is essential to properly separate areas designed for speech intelligibility from those that require speech privacy. Additionally, consider that acoustics also aid the blind in navigating the workplace environment. Reference the American Disabilities Act (ADA) and Architectural Barriers Act (ABA). SupportinG behavioral chanGe for acouStical comfort Behavioral change requires more than new workplace rules. Supports should include an integrated suite of approaches that support mobility as well as productive work in individual workstations. The overall workplace strategy to achieve acoustical comfort should include the following: • Technologies: Provide mobile technologies that enable workers to move easily to a new location. This includes laptops, smart phones, Voice over Internet Protocol (VOIP), wireless connectivity, and ample plugs for computers. Also provide phone headsets for people who need to take calls at their desk and noise cancelling headsets for those who do not want to move to a new location in order to concentrate. • Space: Provide small focus rooms or shared quiet areas (such as a reading room) where workers can focus without distractions. When zoning space, allow for choice in workstation location. Some people are better able to screen out distractions than others. Those most bothered, should be located in spaces farthest from noise generating activities. • Policy: Allow eligible employees to work from home or from another location when they have tasks that require intense focus. • Protocols: Work with employees to develop protocols to help adaptation to the open office. Frankly “airing” the potential problems alleviates many workers from the fear of appearing impolite which may keep them from registering by having agreed upon, public protocols (See an example protocol in Table 1.) January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 16 WHat: BeHaVIor WorkS–the Human element of acoustics table 1. example protocol for behavioral adaptation These actions should be discussed in an all-hands forum to maximize understanding and acceptance. Speak in a low, normal voice. (This is easier when one can see Limit conversations in the open workspace; hold meetings other occupants of the space rather than in the fictional privacy behind closed doors or in public spaces away from the open of a “cubicle” with high partitions.) workstations. Be particularly aware of workers who are adjacent to main circulation paths. Keep phone conversations short or move them to an enclosed room. (Rooms for these kinds of calls need to be convenient Be aware that lengthy hall conversations before and after and not “out of the way,” or workers will not use them). meetings can be heard by desk workers nearby. Where possible, locate conference room entries away from Schedule lengthy calls for enclosed rooms with speaker workstations to allow communication that occurs before and phones. after meetings. If you know you will need access to a computer during a Look before you interrupt; if someone appears to be scheduled call, plan to use your laptop which can be moved concentrating, come back later or use an alternative means readily to an enclosed room. to communicate such as e-mail or mail chat features. Do NOT use speaker phones at your desk in the open office. Avoid noise spill by closing meeting room doors, especially If needed, headphones with voice piece are an acceptable when meeting rooms are located adjacent to the open plan alternative if the voice can be kept at a normal level. work areas. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 17 WHere: Zoning and designing Workplace neighborhoods viSualiZinG acouSticS - acouStic topoGraphieS Graphics such as those illustrated in Fig. 7 at right help to visualize the invisible energy embodied in sound. The acoustic environment can be described as a “topographic” map where spikes of “noise” become very apparent. The diagrams at right show office noise measured in decibels (dB) and translated into different intensities of color. They illustrate both the impacts of “interaction noise” and the opportunities for mitigation using solutions described in Sound Matters. From an organizational and planning perspective, the topographical map in Fig.1 on page 5 and those at the right in Fig. 7 reveal ways to consolidate noise sources to create larger ‘neighborhoods’ of blue low-noise areas for people who require more quiet for concentration. The diagrams also show that mitigation strategies used in the open plan spaces (e.g., improved absorption and masking) can reduce sound levels and improve speech privacy. The specific solutions are described in subsequent sections. The acoustic topography diagrams shown on this page illustrate both the impacts of “interaction noise” within the environment and the opportunities for addressing those impacts through the guidelines defined in the front section. Note that in each case the background (acceptable) acoustic environment is illustrated in blue and “noisier” areas are shown in varying shades of red depending on the noise level. From a design and organization perspective it becomes clearer how to consolidate noise generators so that the blue areas of less acoustic impact can become larger. The acoustic environment can be mapped topographically using decibel (dB) levels as the vertical measure. The dB sources modeled in these diagrams are those commonly found in the contemporary workplace: speaker phone use in the conference room; the loud person standing up talking on their cell phone; normal speech at one’s desk; socializing in the break room. Acousticians predict voice privacy levels by understanding the decibel level of the voice relative to the ambient noise levels in the work environment. The coloration of the diagram below shows the areas where normal voice privacy is achieved (blue areas) and is not (red areas). fiG 7. improvinG noiSe levelS at the WorkStation The background (acceptable) acoustic environment is illustrated in blue while “noisier” areas are shown in varying shades of red depending on the noise level. By addressing the impacts of “interaction noise” discussed in these guidelines, noise generators can be consolidated so that blue areas of less acoustic impact can be increased loud Quiet before after January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 20 WHere: Zoning and designing Workplace neighborhoods the baZaar and the library: fiG 8. analoGieS for the contemporary office tWo exampleS of different acouStic SettinGS During the acoustics charette in Washington DC, one participant characterized the difference between the interactive/noisy mode and the concentrative/quiet mode as similar to behaviors in a library or a bazaar. The contrasting needs of the modern workplace can be seen as “The Bazaar” and “The Library,” with different acoustic needs and responses appropriate for each. In the recent past, workplace designers have conceived of all workplaces as libraries. What is the traditional workstation if not a library carrel grown large or a fictitious room (with corresponding fictitious privacy)? But the library approach is often is at odds with the collaborative (bazaar-like) activities which are also integral to the current workplace. Like a thriving urban environment, workplaces need both “bazaars” and “libraries.” One is not “better” than the other. Expectations of noise and speech privacy differ according to whether a workplace area is meant to function more like a bazaar or a library. For instance, as Fig. 8 at right shows, a range of behaviors are expected even within the library and the bazaar. “the library” is an analogy for a workplace environment where both quiet and speech privacy are expected to optimize the ability to concentrate. Sound masking is designed to ensure sound privacy but sudden outbursts would be considered inappropriate and disruptive. If a space is too quiet, even low speech level can be understood and can disrupt. “the bazaar” is an analogy for the expectation that the area is not private, where sharing is the norm even though sound masking helps to ensure an acceptable level of speech privacy for work. Noise is far more acceptable to workers in the bazaar and a high level of intermittent background noise is expected. In fact, what workers overhear can lead to an improvement in their job competencies. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 21 interruptible/ Some diSturbance acceptable all-handS preSentation/ lecture Speech WritinG/ preSentation preparation/reSearch brainStorminG/critiQue data analySiS/Spread SheetS Work “Organic,” creative, nOn-rOutine tasks Mechanical, Routine tasks “t h e l ib r a r y ” “t h e b a Z a a r ” fiG 9. a fine-Grain look at locatinG activitieS in the contemporary office Zoning work activities minimizes acoustic obstacles to high performance non-interruptible/ loW diSturbance level WHere: Zoning and designing Workplace neighborhoods Fig. 9 is a more detailed consideration of “the library” and “the bazaar” together with the kinds of tasks that might be further zoned to allow optimal effectiveness of the workforce by providing an environment that conforms to both the nature of the work and the worker’s expectation. As shown, a “bazaar” zone can have both highly interactive brainstorming functions or less interactive presentations and lectures. Given the variation in function, the zoning approaches will vary. Similarly, a “library” zone needs to support quiet work which can range from intense concentration to work that is more routine. A good designer realizes that there are subcategories within the large framework that allow the space to be tailored to support the work. Acoustical comfort is neither expensive nor difficult to achieve, provided that it is recognized as a key consideration at the planning and design stage of a project. Acoustic mitigation becomes much more expensive and difficult to retrofit after build out. The first step is to identify the balance of interaction and concentration needed for a work group’s effectiveness. PBS has developed a survey methodology to facilitate workplace design that supports the nature of the work housed in the space. The PBS methodology is based on how mobile or “desk-bound” workers are, as well as how much workgroups either interact or need to concentrate. PBS’s Workplace Solutions Library (WSL) discusses how these “work patterns” form the basis of a rational approach to workplace design. The matrix on the next page (Fig. 10) illustrates the criteria for the 6 work patterns that result from this analysis. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 22 WHere: Zoning and designing Workplace neighborhoods neiGhborhoodS and Group oWnerShip Creating neighborhoods provides a number of acoustic advantages. First, it is easier to isolate sounds to a specific area if the neighborhood is properly sized. Other mitigation strategies – such as spatial separation – can be used to define neighborhoods. Second, neighborhoods make it easier to create a feeling of “ownership” that allows people some control over activities in their environment. The more a neighborhood is comprised of a single business group, the greater the ability to control activities and the acoustic environment. If residents are from unrelated groups, there generally will be less sense of ownership or control over the acoustic environment. fiG 15. acouStic deSiGn and ZoninG detailS a DESK-BOUND INTERACTIVE a b c iNTERNALLY-MOBiLE iNTERACTivE e d EXTERNALLY-MOBiLE iNTERACTivE a For the interactive deskbound groups, acoustic “clouds”, or baffles, over informal meeting areas should be considered for greater speech privacy. b Higher panels give the illusion that the worker is “alone” and, as a result, voice level tends to rise. Interactive work patterns benefit from lower panels. A survey of 24,000 occupants by the Center for the Built Environment shows that in practice, there is virtually no difference in user satisfaction between low and high partitions. c Shielding occupants from constant eye contact (seated privacy) will increase the ability to concentrate and will discourage disruptive idle chatter that is not related to the work. But higher than 51" is not recommended – low panels increase acoustic performance by making workers aware of others in the work space. d Conference/focus rooms not only serve the necessary collaboration needs of the 21st century office, but also provide breaks between the interactive and adjacent, more quiet environments. Consider acoustic treatment on vertical surface per P-100. e Provide an area near the interactive area for those times when a worker needs to do a more concentrative task. When a quiet area is to be shared with others, no phones are provided and even a sign indicating “quiet area” is a good practice. Panels to provide seated privacy may be included. (No higher than 51" recommended). January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 25 GSA Public Buildings Service U.S. General Services Administration Social Security Administration MetroWest 39 findings wOrksTaTiOns The existing workstation configuration for all employee and manager levels are problematic for a number of reasons. 1. PCs and monitors are placed in the inside corner of the workstation. Staff need dual monitors. 2. This orients the user away from the circulation and spaces external to the workstation, with the user’s back to the aisle. 3. Voices are focused inwards, towards adjacent workstations. 4. Air circulation is poorest at the interior corners, and is aggravated by 72’ high workstation panels. 5. Users are too close. 6. Passersby are able to see monitors and worksurfaces without user’s awareness due to the location. 7. The high workstation panels create several additional problems, including a false sense of acoustical and visual privacy. This results in louder voices and careless oversight of sensitive information. 8. Poor ergonomics - no specifications standards for staff with disabilities. 9. Panel system is inflexible not conducive to change 10. Corner units determine placement of the computer monitor and waste space. GSA Public Buildings Service U.S. General Services Administration Social Security Administration MetroWest56 reCOMMendaTiOns wOrksTaTiOns Without significantly changing either the footprint or functional requirements of the existing workstation, the occupant’s individual environment would be greatly be improved with the following strategies. 1. Reconfigure the workstation so that the primary work surface is oriented outwards, away from the internal workstation corner. 2. PCs and flat screen monitors should be placed on the outside corner of the primary work surface (preferably on adjustable monitor arms to keep work surface clear). 3. Voices are focused outwards away from adjacent workstations and towards buffer areas (aisles, shared workspace). 4. Air circulation is improved with lower panels and outward focus. 5. Outward focus spaces users further apart (at the edges of the workstation), improving both acoustical and visual privacy, and enhancing user oversight of information. 6. Lower panels at the primary work surfaces allows greater visual connection between workstation occupants and managers, enhancing individual connection to the group and improving supervision. 7. Clusters create a connection to groups, a minimal requirement is needed to make the changes. 8. Ports for managers to plug-in headsets at desktop phone height. fiG 16. acouStic deSiGn and ZoninG detailS Other partitions for offices and conference rooms, STC 40-45. Acoustic treatment on vertical surfaces recommend to increase sound absorption. Attenuate open plenum return diffusers. High isolation: slab to slab (caulked at sill and head).The partition achieves a minimum of STC 53. This high level of isolation is more expensive than some other partitions, but may be necessary to allow for concentration. Personnel costs far exceed the cost of this mitigation! (Example justification: workplace next to child care or cafeteria). Minimum: sound absorption of enclosing workstation partition: 0.8 NRC Workstation, maximum 66" tall, with seated privacy recommended at 51" maximum. Use of glass panels above 51" strongly recommended (this will achieve 1 LEED interior point; possible additional points for even lower partitions, see LEED). Speaker phones in open areas not provided and should only be located in enclosed offices and conference rooms with STC 45 min enclosures. Locate entrances to conference rooms away from work areas, especially where large groups may be able to congregate before entering. a b c d DESK-BOUND CONCENTRATIVE e iNTERNALLY-MOBiLE CONCENTRATivE EXTERNALLY-MOBiLE iNTERACTivE b a c d e fiG 17. WorkStation arranGement The arrangement of workstations shown at the top illustrates the problem of laying out workstations so that occupants are speaking “at” each other. Positioning workstations as shown on the bottom will improve this acoustic challenge. 5’ 6’ 0” 8’ 6 ” 6’ 0” 5’ 2 3 1 4 5 6 7 9 a is le 8 7 10 9 6’ – 8’ 6’ 0” 8’ 6 ” 6’ 0” 8’ – 9 ’ 2 3 1 4 5 6 a is le 8 6 8 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary OfficeJanuary 2012 26 WHere: Zoning and designing Workplace neighborhoods WHere: Zoning and designing Workplace neighborhoods location choice / mobility proGramS People now work in a variety of settings within the office or externally as their tasks and activities change. The more choices in settings at work, the easier it is to either move noisy activities away from others or for an employee to move to a quiet area. These behaviors require mobile technologies (e.g., wireless connectivity, mobile phones, laptops, phone headsets) to be successful. This mobility allows staff to avoid one of the greatest obstacles to workplace effectiveness: distraction arising from the use of conference calling from the workstation in an open office environment. Another antidote to speaker phone conference calls in the open office: focus rooms. Courtesy of DEGW Alternative working areas away from a workstation can be used as needed and are characteristic of the new workplace. They allow employees to avoid distractions or keep them from distracting others. Mobile Workers are not adding to the acoustical distractions in the office. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 27 HoW: technical tips for Physical acoustic Mitigation cover (MASK) Most contemporary open workspaces are simply too quiet to be acoustically comfortable. Though this seems counter-intuitive, a low level of background noise allows interruptions to contrast with the quiet, causing a greater distraction than if the space had a higher level of background noise. To create the low-level of continuous and unobtrusive background sound that is essential for acoustical comfort and speech privacy, a “sound masking” system is required. There are many types of masking systems available, ranging from a tabletop fountain to complicated in-plenum electronic systems with multiple time of day settings. Minimize HVAC background (BG) and provide masking to make BG uniform. The US Access Board does not have any information on masking sound and how it affect access for the disabled both the hard of hearing and blind. Some activities and spaces may require more or less sound masking than others. There are myriad ways to provide sound masking – to individuals, groups, or to large areas or with a single-function. Sound masking methods include ceiling based applications, desktop systems, or apps (downloads) for your mobile phone or laptop. “Personalized” sound masking at a specific workspace is also possible with new technologies. Given very specific acoustic needs at particular workspaces the options are available to create a focused “cone of silence” or to keep discussions from being understood nearby. Because there are so many types of masking systems available, it is important to be specific about your requirements. For example, some work areas are well- suited for paging and music, while others are not. All sound masking systems today can be tuned to respond to specific workspace acoustic situations (see the images in the topographic maps: Fig. 1 and Fig. 7, as an example of differing situations). Through the programming and design process, specific workspace areas that create different acoustic environments can be identified. Tuning the sound masking system allows for adjustment of these areas to create the best overall environment. The chart on the following page (Fig. 18) shows how absorbing, blocking and covering (masking) can be achieved in closed versus open offices, depending on the level of confidentiality required. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 30 fiG 18: Summary of Sound mitiGation StrateGieS Sender path receiver receiver is at the mercy of the sender– absorb But when the sender can see the receiver (and interpret Surfaces which absorb sound, particularly in the ceiling* their body language) the sender will typically modulate diminish the strength of the sound from the sender as it their voices. In a 24,000 subject survey by the Center travels across the path to the receiver. Walls and floors for the Built Environment (CBE), these were the most are also potential sound absorbers. With reflective floor satisfied workers in terms of acoustic comfort. The finishes, such as marble, footfall can be especially CBE researchers hypothesized that greater voice annoying to workers. modulation was the result of greater visibility of others in the environment. *since it serves as a reflector block (inadequately) This is the typical way that high workstation partitions are arranged and it illustrates why this arrangement is doubly ineffective: 1) Sound, being like water, leaks into the receivers’ work area and 2) the sender cannot visually gauge the effect of their voice level on coworkers who are not in their line of sight. block The strategy illustrated is very effective and very expensive. It requires that the ceiling be interrupted, requiring significant labor since the partition continues to the structure above the ceiling. Where the partition only stops at the ceiling which is typical commercial office construction, the blocking action is not nearly as effective because sound leaks are inevitable at the ceiling plane. cover (Mask) Another important mitigation available for the open workplace is to supply additional sound, either through “white noise” or background noise such as mechanical equipment, which counteracts the typical quietness of a modern, open workspace. Masking helps to cancel the sound disturbance emanating from the sender. HoW: technical tips for Physical acoustic Mitigation January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 31 HoW: technical tips for Physical acoustic Mitigation acouStic treatmentS for Specific elementS “clouds” – Occasionally, spaces have sound absorbent three dimensional “clouds” that hang from the ceiling. Designed properly in terms of shape, material and location, they provide additional sounds absorption within a space. Put in strategically targeted locations, they can be very effective in quieting naturally noisy activities. “flags” – Similar in style to the clouds, materials can be used that hang perpendicular to the ceiling to accomplish the same sound absorption. Traditionally these were often brightly colored materials that serve to liven up a space or carry wayfinding clues. Sound absorptive materials are available today that are translucent so that they do not block important light within the space. configuration – Configuration is an important tool that also addresses sound transmission paths. For ease of construction, space planners and designers tend to layout offices under the straight and rectangular theory. Adding elements that are not straight and rectangular can contribute to noise loss within a space. To be effective this approach needs to be a joint effort between the designer and the acoustic engineer. doors – Having doors on rooms is important for good acoustics. So is the design of the doors themselves. Butt Hinge Doors – These have the potential to be very good with solid or insulated core. The undercut should be shielded in some fashion such as a sweep or drop seal gasket. Hollow core are only good to poor. The perimeter seal should be three sides and continuous closed cell foam. Results are poor if ‘buttons’ are used as impact stops or none at all. “Barn” Doors – These can be very good if the door itself is solid core or insulated. The sloped upper track in combination with bottom seal and leading edge receiver box makes a very good door. However it is essential that operation is quiet and that there is proper gasketing. Sliding Doors – Largely these are glass and do not have a high STC rating. Parallel top and bottom tracks do not seal as well as the barn door, which provide a good acoustic result. Pivot Doors – Also generally glass with low STC rating. They have gaps on all four sides which makes them a poor choice for acoustical purposes. Irregular, curved or angled walls can help mitigate unwanted sound reflections. This principle is useful for the design of conference rooms and walk up service windows. In these kinds of spaces, parallel reflective surfaces much more easily transmit sound to the opposite side of the room in a way that is distracting. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 32 HoW: technical tips for Physical acoustic Mitigation typical dryWall detailS to achieve Sound blockinG normal privacy room treatmentS These rooms, typically offices, provide privacy, i.e., using normal voice level, conversation cannot be understood. a. Partition is full height, slab to slab, and sealed air tight all around, studs spaced 16-inches on center b. 3 5/8" metal channel studs c. 3-inch thick batts in stud cavity d. 1 layer of 5/8" thick gypsum board on each side; seal joints (see Partition Type 1) e. Sound absorbing panels on 25% of two adjacent walls with a minimum absorptivity factor (NRC) of 0.8 (per P-100) f. With 20 gauge studs, STC 40 (see Partition Type 1) partition type 1: SinGle-Sheathed Sound-rated partition private meetinG room treatmentS a. Partition is full height, slab to slab, and sealed air tight all around, studs spaced 16-inches on center b. 3 5/8" metal channel studs c. 3-inch thick batts in stud cavity d. 2 layers of 5/8" thick gypsum board on each side e. Sound absorbing panels on 25% of two adjacent walls with a minimum absorptivity factor (NRC) of 0.8 (per P-100) f. With 20 gauge studs, STC 45 (see Paritition Type 2) partition type 2: double-Sheathed Sound-rated partition conference room treatmentS (confidential) a. Partition is full height, slab to slab, and sealed air tight all around, studs spaced 16-inches on center b. Double wall 3 5/8", 20 gauge metal channel studs c. Can be done as single wall with isolation with resilient channel on one side (see Partition Type 3) c. 3-inch thick batts in stud cavity d. 2 layers of 5/8" thick gypsum board on one side e. Sound absorbing panels on 25% of two adjacent walls with a minimum absorptivity factor (NRC) of 0.8 (per P-100) f. Minimum 50% of ceiling treated with minimum NRC 0.8 material g. Wall is rated STC 53 (see Partition Type 3) partition type 3: reSiliently-iSolated Wall January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 35 HoW: technical tips for Physical acoustic Mitigation fiG 20. detailinG the acouStic environment GSa p100 acouStical reQuirementS General topicS 1. Sound Isolation 2. Maximum Background Noise - Ventilation Systems - Electronic Sound Masking 3. Room Acoustics 4. Speech Privacy 01: open plan WorkSpace Background noise: NC 40 maximum “normal” Speech privacy electronic Sound Masking: 45 to 48 dBA Provide absorption of NRC 0.9 minimum on 100% of ceiling Provide absorption of NRC 0.8 minimum on 25% of walls 02: private officeS Background noise: NC 35 maximum “normal” Speech privacy Minimum noise reduction of Partitions: NIC 35 (with sound masking) NIC 40 (without sound masking) electronic Sound Masking: 40 to 42 dBA Provide absorption of NRC 0.8 minimum on 25% of walls 03: private officeS “confidential” Speech privacy Background noise: NC 30 maximum noise reduction of Partitions: NIC 45 minimum Provide absorption of NRC 0.8 minimum on 25% of walls 04: teleconference facility Background noise: NC 20 maximum Minimum noise Isolation: NIC 53 Provide absorption of NRC 0.8 minimum on 50% of ceiling and 25% on two adjacent walls optimum reverberation time: 0.5 seconds 05: meetinG roomS, Background noise: NC 25 maximum traininG facilitieS Minimum noise Isolation: NIC 48 Provide absorption of NRC 0.8 minimum on 50% of ceiling and 25% on two adjacent walls optimum reverberation time: 0.6 seconds January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 36 SPeCIaL CondItIonS and neW aCouStICaL treatMentS All materials used in surfaces and furnishings should address sustainability goals. For appropriate materials selections see the GSA Sustainable Facilities Tool (www.sftool.org). The tool is available to the public and is intended for use in small projects that do not normally involve a workplace consultant or designer. While the old ways of solving noise and privacy problems may have been expensive, resource intensive, and required skilled professionals, many of the new materials and solutions are just the opposite. Be sure to ask your planning and design team to research green solutions like the following: • Transparent or translucent glass or plastic partitions that are acoustically absorptive and use light-weight, ‘green’ insulation; • Translucent, light weight, thin and acoustically absorptive surface materials; • Light-weight, acoustically absorptive materials that can be used as design elements (clouds, banners, artwork, etc.) to enliven the workspace while contributing to acoustical comfort and privacy; • New sound-absorbing or vibration-absorbing carpet and flooring material configurations that transform designers’ thinking about ‘green’ flooring and associated maintenance issues; • Low-voltage multi-function distributed audio (sound) systems that conserve energy and cut expense by integrating ‘masking’ (speech privacy) into normal, high-quality sound systems already required for paging and music; • ’Personal privacy’ (masking) products available for the desktop from drug stores, furniture companies or from online retailers; • Even privacy apps you can download to a cell phone and play through ear buds! acouStical treatmentS in hiStoric buildinGS Many federal agencies occupy historic buildings which pose particular acoustic problems due to the extensive use of hard reflective materials especially in the ceremonial spaces which typically adjoin work areas. These hard surfaces, such as marble and plaster, can be very hard to deal with since there is little possibility of absorption without change to the historic fabric. It is all the more important that adjacent work areas are well conceived in terms of sound absorption. At the San Francisco U.S. Custom House, PBS worked with the Regional Historic Officer’s approval to experiment with absorptive panels mounted on walls with clips in one room (see Image A), as well as stretched acoustic material at the ceiling (see Images B & C). To hear the difference in untreated versus treated rooms reference the Acoustic Materials Demonstration Video available via email request at [email protected]. b a c before after: Stretched acoustic material applied to ceiling January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 37 fiG 21: coStS The reader should bear in mind that these costs have been prepared by a professional cost estimator in July, 2011. The costs are based on specific products typical of the class. These costs will vary. What is most important to take from the chart at right is the relative comparison of costs to each other so that decision-makers can judge the cost of acoustic mitigation. Remember that personnel costs dwarf these figures and acoustic comfort is key to getting the best out of employees in the workplace! c o n S t r u c t io n d e S c r ip t io n c o S t Baseline Partition Partition Type #1 Partition Type #2 Partition Type #3 Sound absorbing Lay-in Lay-in Sound masking wall panel acoustical tile acoustical tile system ceiling in 2x4 grid ceiling in 2x4 grid 12’ high 20 gauge Same as Baseline Same as Partition Same as Partition NRC 0.8 minimum Celotex BET-197 Capaul Nubby Logison studs slab to slab, Partition plus R-11 Type #1 plus one layer Type #2 except only NRC 0.55 NRC 0.9 24” o/c, 5/8” gypsum fiberglass insulation, of 5/8” gypsum board one layer of gypsum board each side, Level in stud cavity. Wall added on each side. board on one side 4 finish, painted. penetrations and STC 45 and 1 3/8” resilient Baseline partition is perimeter sealed with channels isolating not sound rated. acoustical caulking. gypsum board on the Low voltage devices other side. placed in outlet boxes. STC 53 All electrical outlets sealed with outlet box pads. STC 40 $154.30/lineal foot 15% more than 31% more than 3% less than $22.30/sq.ft. installed $5.42/sq. ft. $6.97/sq. ft. $1.81 per sq. ft. $12.86/sq. ft. Baseline Partition Partition Type #1 Partition Type #2 Installation of 28% more than installed $176.69/lineal foot 50% more than 45% more than grid and tile, not standard acoustical $14.73/sq. ft. Baseline Partition $231.66/lineal foot Baseline Partition  $224.56/lineal foot including lights, sprinklers, etc. tile ceiling $19.30/sq. ft. $18.71/sq. ft. Refer to page 35 for full-scale versions of the details shown as thumbnails above. STC ratings shown here are derived from Canadian Sheet Steel Building insititute Refernce Report iRC-iR-761 and veneklasen Associates testing at Western Electro Acoustics Laboratory. PuttInG It aLL toGetHer: Costs January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 40 referenCeS reSearch reSourceS Acoustical Society of America, www.asa.aip.org Beranek, L.L. Noise Reduction. New York: Wiley, 1960. Cavanaugh, W.J., G.C. Tocci, J.A. Wilkes. Architectural Acoustics: Principles and Practice. 2nd ed. New York: Wiley, 2009. Canadian Sheet Steel Building Institute. Reference Report IRC- IR-761 and Veneklasen Associates testing at the Western Electro Acoustic Laboratory Egan, M.D., Architectural Acoustics. Fort Lauderdale: J. Ross Publishing, 2007; originally New York: McGraw Hill 1988. GSA PBS P-100 Acoustic Standards Heerwagen, J., K. Kampschroer, K. Powell and v. Loftness. “Collaborative Knowledge Work Environments”. Building Research and Information Nov-Dec 32(6) (2004): 510-528. Heerwagen, J., K. Kelly, K. Kampschroer and K. Powell. “The Cognitive Workplace”. Creating the Productive Workplace. Ed. D. Clements-Croome. London: Taylor & Francis, 2006. Institute of Noise Control Engineering of the USA, www.inceusa.org Jensen, K.L., E. Arens and L. Zagreus. “Acoustical Quality in Office Workstations as Assessed by Occupancy Surveys”. Proceedings of Indoor Air, 2005. Johnson, Steve, quoted in the Colorado Real Estate Journal, August 6-9, 2008. Used with permission of the author. Rashid, M., K. Kampschroer, J. Wineman and C. Zimring. “Spatial layout and face to face interaction in the office.” Environment and Planning B: Planning and Design 33(6) (, 2006): 825-844. Zijlstra, F.R.H., R.A. Roe, A.B. Leonara, and i. Krediet. “Temporal factors in Mental Work: Effects of Interrupted Activities”. Journal of Occupational and Organizational Psychology 72 (1999):163-185. January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 41 u.S. General ServiceS adminiStration public buildinGS Service 1800 f Street, nW WaShinGton, dc 20405 WWW.GSa.Gov acknoWledGementS The Center for Workplace Strategy would like to particularly acknowledge the editing assistance of Judi Heerwagen and Michael Bloom of GSA’s Federal High Performance Green Building, as well as David Sykes and Bill Cavanaugh for their “above and beyond” help in editing this document. In addition, the core team of Charles Salter (Charles Salter Associates) and Paul Heath and Clark Sept of Business Place Strategies. Thanks also to the Gensler team for the acoustic diagrams and help with the final design. GSa Michael Bloom Patricia Cheng Judith Heerwagon Diane Juba Kevin Kelly Kevin Powell business place Strategies Paul Heath Clark Sept charles m. Salter assoc. Charles Salter Gensler Gervais Tompkin haworth Jay Brand place coach Sally Augustin ia interior architects R. J. Brennan ideo Beau Trinicia arup Nick Antonio brc acoustics Dan Bruck acoustics research council David Sykes armstrong Ken Roy uS Social Security administration Donna A. Ellis uS State department Thierry Rosenheck uS coast Guard Leo Lozano January 2012 Sound Matters: How to Achieve Acoustic Comfort in the Contemporary Office 42