Sound Advice: Office Acoustics

Noise Cancellation vs. Sound Masking

2009-06-18T14:23:00.011-04:00

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

2009-05-21T14:05:00.004-04:00

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"

2009-04-30T14:21:00.021-04:00

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?

2009-03-17T13:16:00.026-04:00

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

2009-02-26T13:42:00.012-05:00

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?

2007-05-22T14:10:00.004-04:00

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

Open Office Plans - Sound Masking is Important

2007-03-22T10:14:00.000-04:00

Open office environments, like almost any other human space, suffer from an acoustical conflict.

On the one hand, we require an environment where we can effectively communicate with our coworkers. This means we must allow for clear vocal transmission between individuals. On the other hand, we only want our vocalizations to reach their intended target, rather than to the office at large. Unintended noise transmission is distracting and ultimately leads to low worker productivity, among other things.

Open office plans have the potential to be an acoustician's nightmare, but with proper planning and foresight they can become successful acoustic environments. Appropriate building materials, furniture, and partitions play a critical role in acoustic quality. Sound masking is an equally important, but frequently overlooked, element of successful acoustical design:

"Sometimes overlooked by facility executives, a sound masking system is invaluable in an open office space... No matter how acoustically well-planned a space's floor, ceiling, furniture panels and finishes are, a correctly configured sound masking system will always improve speech
privacy." ("Sound Decisions," Building Operating Management, January 2007)

Also important to note is the necessity of professional tuning and calibration of a sound masking system:

"One of the biggest mistakes... facility executives make is installing and tuning a sound masking system themselves... People buy canned units and don't take time to address the whole open plan space. Masking needs to be something that's thought out and planned carefully."

Office of the Future?

2007-03-15T16:58:00.000-04:00

What does the "office of the future" hold in store for us? Will it be bright and colorful, sleek and shiny, or modern and sterile? What will our work flow and work patterns be like? Will we work more independently, or will we tend towards collaboration?

Popular Science attempts to answer these questions ( "The Future of Work," March 2007) with an article chock full of gizmos and gadgets that may make an appearance in the office landscape some time soon. Included in this list of gadgets is the new "Babble" device, which "scrambles the sound of your voice and transmits it over a speaker to render your words nonsensical to eavesdroppers." This hardly sounds like something to look forward to, considering the already high levels of distracting noise in most office environments, and the trend towards fewer traditional sound barriers.

The article then goes on to mention the benefits of sound masking in this new environment:

"Less distracting is a ceiling-mounted noise generator... a system of small speakers that issue a sound-masking whoosh not unlike the sound of an air conditioner."

Technology will certainly be evolving along with the workplace, but I think the real question is: will it make work more productive, enjoyable, or rewarding? What will be the human benefits of these new technologies?

Personal Sound Masking - Not a Magic Wand

2007-03-15T14:49:00.000-04:00

Everyone who has worked in an office environment has experienced problems with chatty neighbors, noisy hallways, or annoying cell phones. Some employees may find these situations more distracting than others. Cambridge Sound Management's newest device, the Sonet Qt, proposes to treat these problems on an individual basis, using spot acoustical treatment. The device seems to be appropriate for situations in which one particular individual is having difficulty with acoustics, rather than as a broad spectrum, facility-wide treatment.

Synopsis of product review of the Sonet Qt in Buildings magazine:

"It's ideal for 'spot treatment' in situations where one individual is distracted by voices, outside traffic, or other noises... [The] Sonet Qt is not a facility-wide system. Instead, it provides soundmasking on an as-needed basis to a select number of individuals who may want (or need) it."