Learn more about office design and acoustics

Would you like to learn more about office acoustics and proper acoustical design? CCR ASSOCIATES has posted an educational resource, Guidelines for Design of an Office with Good Acoustics to help office designers, architects, and facility managers better understand office acoustics. This book is free to download.

Table of Contents
Chapter 1: Privacy Concepts
Chapter 2: Speech Privacy
Chapter 3: Achieving Acoustical Privacy in Open Offices
Chapter 4: Achieving Acoustical Privacy in Closed Offices
Chapter 5: Medical Facilities
Chapter 6: Secure Facilities
Appendix: A Primer on Sound Masking

You can also download the entire book here.

Office Acoustics in a Green Building

Office acoustics and green building trends - can they play nice together? CCR ASSOCIATES' own Charles Roy was recently quoted by an article in Buildings magazine regarding this topic:

Both the design of an office space and its materials should be carefully considered to address the ABCs (absorb, block, and cover) of acoustics; this has proven effective for ensuring speech privacy for years. According to Charles C. Roy, president, CCR Associates LLC, an Essex, CT-based acoustical consulting firm, "… the absorption (ceilings, furniture, and carpet), blocking (walls, furniture, and ceilings) and covering of sound (controlling the ambient background with soundmasking) are critical components in addressing office acoustics. In general, when one segment or another is ignored, the cumulative outcome for speech privacy will be less than when all are addressed equally."...

LEED and other green building techniques can, without foresight, have a detrimental effect on office acoustics. However, so can many other building practices, green or not. With proper design and attentiveness to the ABCs, green offices can indeed "play nice" with acoustics.

Setting the Stage for Speech Privacy

It pays to keep a common sense approach to office acoustics. There are numerous practical and economical ways to cut down on unwanted noise transmission that are not only highly effective, but necessary first steps towards building a desirable acoustic environment. Remediation strategies such as electronic sound masking can only be effective if the underlying structural environment is relatively sound.

As acoustical consultants, CCR ASSOCIATES is frequently called in to assess ongoing acoustical problems in currently occupied office space. Once on site, it often becomes apparent that many acoustical problems are due to structural/design problems in the office, and that these design problems must be resolved before one can accurately assess the potential effectiveness of sound masking. Wall and ceiling voids, open air grills, low/no cubicle walls, poorly sealing doors and windows, poorly designed workstations, etc. are all very common. Common sense dictates that sound will transmit through openings, and that these openings should be sealed, if possible.


The chart above demonstrates how important it is to fix any underlying structural acoustical problems before attempting further remediation. Until an office reaches a Privacy Index of 60 or above, little acoustical benefit can be gained from sound masking or other electronic acoustical remediation. Above 60, increases in PI through sound masking or other means are considerably more effective.

Noise Cancellation vs. Sound Masking

Though the terms are often used interchangeably, noise cancellation and sound masking utilize different technologies and are used for different purposes.

Technically speaking, it is nearly impossible to truly "cancel" noise in a typical human environment, due to the highly variable and dynamic nature of most living and working space. However, you can come close if you are able to isolate and control the noise from the greater environment. Headphones are frequently used for this purpose. Settings in which the ambient sound frequencies are relatively static and easily predicted, such as on an airplane, or close to a particular machine, are appropriate for noise cancellation technology. Noise canceling headphones or speakers assess the current ambient sounds, and generate a tone with the inverse wavelength, which in effect cancels out all sounds of the targeted wavelength.

Homes, offices, stores, and most other human environments display a highly dynamic range of sound frequencies, making it very difficult and costly to monitor and cancel frequencies in the manner of typical noise cancellation technology. Also, it is beyond the scope of most if not all existing noise cancellation technologies to differentiate between undesirable background noise (chatter), and useful human vocalization (desirable communication). It would clearly be unhelpful to cancel or otherwise scatter all human speech in a home or office.

Sound masking masks (as the name implies) rather than cancels sounds. You have probably experienced the effects of sound masking in your home when you stand at the kitchen sink with the water running, and try to talk with someone across the room. The sound of the running water makes it difficult to clearly understand the person talking. Once you turn the tap off, you can once again hear the conversation clearly. Running water masks human speech very well, without distracting or annoying the listener, because it creates a random, yet relatively uniform sound, within a specific frequency spectrum.

To be effective, sound masking systems must generate sound that is both random and within a specific range of frequency and decibels. Typical humans will actively listen to sounds that form a recognizable pattern, like music or speech, but will tune out sounds that they can't make sense of, like static (unless the sound becomes too loud). In an office, sound masking works by injecting a random, low-level background noise that correlates in frequency to typical human speech, making it difficult to understand conversations outside of the listener's immediate area. Care must be taken to insure that both the decibel level and frequency of the sound masking system is appropriate for the environment. If the sound masking is set too loud, or at the wrong frequency, occupants may have a negative response.

To set the sound masking to the appropriate levels, the office must first be assessed for it's existing acoustical qualities, which include the size of the office, the physical materials of the office (walls, ceilings, doors, partitions, etc.), the furniture in the office, the number of occupants and their normal functions (customer service, engineers, managers, etc.), typical background noise levels in the office (HVAC, copiers, computers, etc.), and purpose of the office space (quiet work area, team work area, call center, meeting room, etc.). Depending on the circumstances, the system can be tuned for greater speech privacy (for example, a work area that requires mental concentration with little distraction) or lesser speech privacy (for example, a collaborative work area, where employees hold informal meetings as well as work independently).

Measuring Speech Privacy - Guidelines for Success

Though it may seem subjective, speech privacy can be measured, and the overall acoustical effectiveness of an environment can be objectively calculated. Our main tools of measurement are the Articulation Index (AI) and the Privacy Index (PI).

Articulation Index is a measurement of speech intelligibility, taking into account the following factors:

• The spectrum of normal human speech
  
• The sound attenuation (loss in intensity due to sound absorption and dispersal) between talker and listener
  
• The spectrum of background noise at the point of the listener.
  

The range of AI is between 0 and 1, where 0 indicates complete lack of intelligibility, and 1 indicates complete intelligibility.

Privacy Index is a measurement of speech privacy. PI can be derived from the AI measurement using the following formula:

PI = 100(1-AI)

The relationship between PI and AI is inverse (as the AI increases, the PI decreases) and nonlinear. The range of PI is between 0 and 100, where 0 indicates complete lack of privacy, and 100 indicates complete privacy.

With office acoustics, avoid the "quick fix"

It is tempting, when presented with a problem, to turn to the quickest solution. However, when it comes to acoustics in office environments, a "quick fix" often isn't quick or a fix.

The truth is, acoustics can be complicated. Typical office environments have numerous factors which can effect acoustical outcomes:

• Multiple sound sources which fluctuate in volume throughout the day
  
• Multiple surfaces with differing acoustical qualities, including carpeting, ceiling tiles, walls, cubicle partitions, and office furniture
  
• Varying construction methods, including use of demising and partition walls, ventilation and duct work, ceiling type, and lighting
  
• Office size, shape, and layout of work space
  
• Intended use of space (reception area, team work environment, quiet "heads down" work environment, private discussion area, large meeting area, audiovisual area, etc.)
  

Without careful planning it is very easy to add more noise to the situation, without effectively treating the problem. Watch out for "quick fix" remediation strategies, such as plug-and-play "white noise" speakers or other stand-alone products. These strategies are rarely effective, and can often create further acoustical distraction, as without careful calibration it is unlikely the sounds generated would coordinate with the particular set of acoustical factors within your office environment. To accurately measure, assess the effect, and plan for successful acoustics in your office, turn to an acoustical consultant.

Degrees of Speech Privacy: How much is enough?

When it comes to office acoustics, design follows function. Every human space has different acoustical requirements, depending on its purpose. We expect it to be quiet in a library, and noisy at a basketball game. The acoustical design of each space has (hopefully) been tailored to its function. Like libraries and gymnasiums, office space benefits from acoustical design that has been tailored to its specific purpose.

There are five generally recognized degrees of speech privacy:

1. No speech privacy
2. Transitional
3. Normal
4. Confidential
5. Secret

No Speech Privacy

In environments where face-to-face conversation is the major activity, speech privacy isn't typically desirable, since of course the purpose of a conversation is to hear and understand one another. Retail space, restaurants, lecture halls, and reception areas are examples of areas that don't typically benefit from speech privacy.

Transitional Speech Privacy

Transitional levels of speech privacy allow for transmission of auditory information, but make it slightly more difficult to clearly understand human speech. Casual office layouts with mixed use areas (often used to develop a "team" feeling in the office) generally provide Transitional speech privacy. Though it may feel more like home to have a couch and coffee table in the middle of the work area, it will also sound more like home, too. Depending on the office culture, this may not be a bad thing, but it may lead to an unprofessional atmosphere unless carefully planned and monitored.

Normal Speech Privacy

Most office workers find that Normal speech privacy levels help them to focus on their work, without distraction. Normal privacy allows for auditory transmission, but makes it difficult to understand conversations outside of the employee's immediate area. Office areas in which people are typically working alone at their desks will benefit from Normal privacy levels. The majority of office space falls into this category, though there is a large degree of acceptable variance within the Normal range.

Confidential Speech Privacy

In situations where privacy is important, either for personal, professional, or legal reasons, Confidential speech privacy is recommended. Conversations that you would typically have "behind closed doors" require Confidential privacy levels, ensuring that human speech is completely unintelligible to listeners outside of the conversation.

Secret Speech Privacy

As the name implies, Secret privacy levels make it extremely difficult or impossible for outside listeners to overhear a conversation, even with listening devices. Though it may seem like the stuff of James Bond movies, there are situations in which organizations require complete secrecy in order to protect their interests and prevent information leaks.

Don't Forget Your ABCs

It's important to do your homework before making any decisions regarding acoustical design. Too often, a decision is made to purchase individual acoustical components without taking into consideration the total impact of all the acoustical elements in an office space.

The ABCs of acoustics can help you remember how acoustical components work together:

Absorb: Carpeting and acoustical ceilings are generally the first line of defense when it comes to absorbing office sounds and preventing reverberation.

Block: Cubicle panels, furniture, and walls all help to block sound from carrying across a room.

Cover: By introducing a uniquely "tuned" range of low-level sound to the environment, electronic sound masking provides greater privacy by "masking" the sounds of conversation.

What does a LEED office sound like?

LEED is certainly all the rage, and rightfully so. Though "green building" has been around for quite a while, with LEED we finally have a benchmark program with a proven track record of success.

What role do office acoustics play in LEED buildings?

The core purpose of the U.S. Green Building Council (the organization responsible for developing the LEED program) is:

"...to transform the way buildings and communities are designed, built and operated, enabling an environmentally and socially responsible, healthy, and prosperous environment that improves the quality of life."

How do we incorporate acoustics into this overall goal? Let's break it down:

Environmental and Social Responsibility:

On the surface this may seem like a non-issue. We're just talking about sound waves, right? But, as always, there are factors to be considered. Noise pollution isn't just something coming from cars on the highway -- it can also be coming from the copier in the hallway, or the phone ringing in the office next door, or the coworker sitting across from you. Noise pollution = noise where it shouldn't be. Excessive unwanted noise can create a toxic environment for office workers. This leads us to another important aspect of acoustics and the LEED program,

Occupant Health:

Numerous studies have concluded that excessive unwanted noise and lack of speech privacy can seriously affect your health, increasing stress levels, which leads to headaches, high blood pressure, and possible heart disease. Acoustics are an important component of Indoor Environmental Quality, but as yet have been overlooked in LEED certification standards.

A Prosperous Environment:

A successful acoustical environment leads to happier employees, less stress, less sick days, greater speech privacy, and greater productivity. In one study, workers in a noisy office made 40 percent fewer attempts to solve a problem, which amounts to a significant loss in overall productivity. Speech privacy is also important to a prosperous corporate environment -- without it, confidential conversations can become hot topics around the water cooler, or worse yet, lead to dropped clients or potential lawsuits.

Conclusion:

With proper acoustical design, office environments can successfully fulfill the core principles of the LEED program -- environmental and social responsibility, a healthy and prosperous environment, and a general increase in the quality of life.

Resources:

What Does Sustainable Design Sound Like? from Acoustics.com

What is LEED? from the U.S. Green Building Council

Green Audiovisual Systems from Sound & Communications

Research on Indoor Environmental Quality (IEQ) from the Center for the Built Environment