Architectural Record BE - Building Enclosure

Innovations in Acoustical Ceilings for Today’s Flexible Interiors

Total acoustical quality for offices, healthcare facilities, and classrooms
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Sponsored by Armstrong Ceiling and Wall Solutions

The Gensler 2013 U.S. Workplace Survey1 examines “What Factors Drive Workplace Performance?” The company commissioned a nationwide survey of 2,035 professionals to examine the design factors that create an effective workplace.

The results showed that U.S. workers are struggling to work effectively and overall work performance has dropped 6 percent since the last Gensler study in 2008.

As the study reaffirmed, effective workplaces have a balance between focused work and collaboration. Since 2008, the time spent in focused work has increased 13 percent, while time spent collaborating has decreased 20 percent. In the end, choice drives performance and innovation. Giving employees a choice of when and where to work increases their performance.

The solution to workplace performance is in providing effective focus space. The study says: “Design factors that influence the ability to focus most significantly include the functionality of primary space, design look and feel of primary space, and effective noise management.”

To be most effective, workers need to both focus and collaborate, two very different activities that often happen in the same space, with unwanted noise playing a big part in the functionality, or lack of functionality, of the space.

Innovations in Acoustical Ceilings for Today's Flexible Interiors

Image courtesy of Armstrong® Commercial Ceilings

In today’s offices, focus time and collaboration time must often happen within the same open space.

In the Danish-American Acoustic Satisfaction Study2, researchers at Technical University of Denmark and the Center for the Built Environment (CBE) at the University of California Berkeley analyzed acoustic satisfaction of 23,450 survey respondents from 142 buildings on acoustic satisfaction.

The conclusions and implications of the study may be just as alarming to bosses as it is informative to architects and designers:

► Office workers are significantly more dissatisfied with the lack of speech privacy than with the level of noise.

► More than 50 percent of cubicle occupants think poor acoustics interfere with their ability to get their job done.

► Thirty percent of those in private offices say poor acoustics interfere with their ability to work.

► In indoor environmental quality, poor acoustics causes the most dissatisfaction.

► More focus on speech privacy and noise is needed.

The important factor to remember is that buildings are for people. The goal should be to provide a space that is healthy and productive for the occupants, as well as energy efficient and sustainable.

Towards addressing that goal, acoustic comfort means an acoustic environment that provides speech intelligibility for communications and safety, speech privacy for confidentiality, low distractions and annoyance, and good sound quality for recorded and A/V programs.

It's fair to say that current approaches to building design and construction are not meeting the occupants' indoor environmental quality and acoustic needs.

Poor Acoustics Not Adequately Understood

Acoustical design is certainly part of the solution. According to studies by the CBE3, “noise is probably the most prevalent annoyance source in offices, and that can lead to increased stress for occupants.”

The lack of speech privacy, the CBE says, is the most important factor.

However, the CBE states, “Acoustics in most cases do not receive the level of design attention as thermal, ventilation and other architectural and engineering considerations. The causes and consequences of poor acoustical performance are perhaps not adequately understood by designers and building owners.”

In the past, ceilings typically offered either good sound absorption (noise reduction coefficient, NRC) performance to control reverberation and decrease unwanted sound levels, or good ceiling attenuation (CAC) to blocking unwanted sound intrusion into spaces. Now, there are ceilings with combined high NRC and high CAC performance for an ideal combination of acoustical control in one panel.

Because workers spend more time focusing and less time collaborating than in the past, acoustic design becomes even more important to solve noise and speech privacy problems.

It helps to understand a few principles and the terminology used in the acoustic design.

Measures Relating to Sound Within a Space

Noise Reduction Coefficient (NRC)— A measure for rating the overall sound absorption performance of a material when used in an enclosed architectural space such as an office, where sound is being reflected at many angles of incidence.

Specifically, it is the 4 frequency averaged absorption coefficients @ 250, 500, 1000 and 2000 Hz, rounded to the nearest 0.05. A material with NRC < 0.50 (which means it absorbs less than 50 percent of the sound energy that strikes it) is a poor absorber, and NRC > 0.70 (which means it absorbs more than 70 percent of the sound energy that strikes it) is a very good absorber.

Reverberation—The buildup of sound within an architectural space, such as a room, as a result of repeated sound reflections at the surfaces of the room. Exposed structure—those spaces having no ceiling but with exposed building service—will often have noise problems. Sound reflecting off the deck above creates excessive reverberation such that large spaces require sound absorption to reduce distracting noise. There are acoustical treatments available to address these types of spaces.

Reverberation Time (RT)—A measure for rating the quality of the sound environment within an architectural space, and its appropriateness for various uses. Specifically, the reverberation time is the time it takes for reflected sound within a space to decrease by 60 dB after the sound was made. Typically, an RT < 1 second is good for speech intelligibility, while an RT > 2.5 seconds is good for symphony music.

Repeated sound reflections off the room surfaces cause a buildup of sound referred to as reverberant sound. In exposed structures, the MEPs can cause noise problems.

Image courtesy of Armstrong® Commercial Ceilings

Repeated sound reflections off the room surfaces cause a buildup of sound referred to as reverberant sound. In exposed structures, the MEPs can cause noise problems.

Measure Relating to Sound Attenuation (Transfer) Between Open Plan Spaces

Articulation Class (AC)—A measure for rating the speech privacy performance of a ceiling in an open plan environment where sound is reflected off the ceiling between two adjacent spaces divided by partial-height furniture panels. A ceiling system with AC ≤ 150 is low performance, while one with AC ≥ 180 is high performance.


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Originally published in Architectural Record