The Sound of Silence

Feb. 1, 2000
Achieve open-plan privacy through an integrated system of products.

Snoop, eavesdropper, nosey: It’s easy to fall into one of these categories when the open-plan office fails to provide privacy.

Open-plan offices have been hailed for their success in facilitating communication. However, not all of this verbal communication is welcome, especially to employees working heads-down, deep in concentration. It is not the click-click of the keyboard, the sound of the phone ringing, or the whirring noise of the printer that distracts most employees in an open-office environment. It is the human voice, passing and transmitting information, that distracts individuals. When bits and pieces of phone conversations and one-on-one interactions turn into intelligible words and phrases, maintaining concentration on the task-at-hand may become difficult for the occupants of nearby cubicles.

A culmination of the appropriate systems and products will both encourage communication and absorb, block, and cover it (the ABCs of open-plan acoustics) to decrease the number of conversational distractions for autonomous employees. Carpet, high-performance ceilings, the appropriate systems furniture, and an effective sound masking system can recapture lost productivity by up to 30 percent, says Tom Koenig, president of Dynasound Inc., a Norcross, GA-based manufacturer of sound masking systems.

Although rarely recognized for its role in reducing noise in the office, carpet is one of the most frequently employed products that possesses acoustical characteristics, says B.J. Miller, ASID member and president of Johnson City, TN-based Visions Design Group Inc.

High Impact Insulation Class (IIC) and Noise Reduction Coefficient (NRC) ratings indicate a floorcovering’s ability to absorb low levels of airborne noise and reduce sound transmission to rooms below through increased sound insulation, according to the Atlanta-based Carpet & Rug Institute (CRI). CRI studies also show that the NRC of a cut-pile carpet increased by as much as 20 percent with the addition of a high-weight and thick cushion. Cut-pile carpet proved to have a greater NRC than loop pile when tested, as did foam-backed loop when compared to conventional secondary backed carpet.

When words pass from the brain to the mouth and out into the air, some sound waves will inevitably travel over systems furniture panels, striking the ceiling at angles between 45 and 60 degrees. High-performance ceilings are designed to control speech noise from bouncing off the ceiling and reflecting down into adjoining or subsequent workstations. The role of the ceiling “is to control or to absorb high amounts of speech noise at speech frequencies,” says Fred W. Folsom, manager of corporate knowledge at Lancaster, PA-based Armstrong World Industries Inc. In areas where 6- by 8-foot cubicle sizes are the standard, Folsom recommends a 0.90 or 0.95 NRC and an Articulation Class (AC) rating of 200 to 210.

Both the Washington, D.C.-based American Society of Interior Designers (ASID), in its 1996 study Sound Solutions, and Folsom recommend avoiding ceiling-recessed light fixtures with hard plastic lenses. Typically clear or white in color, solid textured plastic louvers are a problem because they reflect large amounts of speech noise back into workstations. “It would negate all that the high-performance ceiling would do,” says Folsom. Parabolic louvers are a common alternative to these hard plastic 2- by 4- or 2- by 2-foot lenses.

Systems Furniture
“Think acoustically, auditorally, or orally,” instructs Dr. Steven M. Brown, senior principal engineer, Steelcase Inc., a Grand Rapids, MI-based manufacturer of systems furniture. Systems furniture appropriately wraps or encloses the workstation to block and absorb sound that might bounce from one area to another, heightening privacy.

A lower panel height will encourage interaction. However, a higher panel height will limit conversational distraction. It is necessary to evaluate what types of activities will be taking place in the workspace, whether the majority of employees are working individually, or if interaction and collaboration are both frequent and necessary.

Panels with a Sound Absorption Average (SAA) of 0.80 and a Sound Transmission Class (STC) of 25 or higher, in combination with other acoustical office systems, according to Brown, will provide executive or confidential privacy. In these instances, co-workers can overhear muffled words but cannot intelligibly understand the meaning or content of spoken interactions. The inhabitants of neighboring cubicles are not distracted.

An SAA of 0.70 or 0.75 and a STC of 19 or 20 will provide normal privacy, in which some phrases will be intelligible, but a co-worker’s conversation will not distract an employee enough to discontinue work.

According to Koenig, “Panel height needs to be 18 to 24 inches above the sound source, and [for] most people sitting in an ergonomic chair the standard mouth is 42 inches above the floor.” Brown also recommends a height of 60 to 65 inches for systems furniture panels.

Sound Masking
New heating, ventilating, and air-conditioning (HVAC) systems run quieter and smoother. The hum of blowing air no longer disguises information contained in phone conversations and confidential office discussions. Sound masking is capable of doing just what its name implies — masking sound. Composed of a signal generator, equalizer, amplifier, and speakers, such a system introduces a low-level electronic sound into the space to cover or mask intelligible conversation. “It sounds much like gentle blowing air out of an air diffuser,” says Koenig.

An effective sound masking system is not detectable. It’s comparable to surround-sound and the location of individual speakers cannot be discerned.

The installation process varies in existing buildings where sound masking systems must be gradually ramped up. Over four to six weeks, the system is turned up roughly 1.5 decibels every Friday night when employees leave. Increases are no longer necessary once the level has been raised to NC 40, or 48 decibels, according to the ASID.
In new construction, the system is installed similarly, with a gradual increase over 15- to 30-foot increments from the reception desk to the open-office space, ensuring that employees are not blasted with sound upon entering any given area. The system can be immediately set to the appropriate level because individuals entering the new building are unfamiliar with its sound. The noise generated from a sound masking system may be mistakenly attributed to a building’s HVAC system.

Additional Factors
People are getting closer in open-plan environments — not emotionally, but physically. Significantly higher workstation densities equal an increase of 30- to 40-percent more employees occupying the same physical space, says Miller. Consequently, there is a greater amount of uncontrolled noise that offices need to accommodate.

The layout of the space will indefinitely influence the amount of speech privacy as well. Numerous visual paths will support teaming, interaction, and a sense of community. However, Brown cautions that the adverse effects of this will be less privacy. A delicate balance must be created to ensure that “a clash of visual and auditory ambience” doesn’t result, he says.

It is equally important to consider how future advancements in technology will affect open-plan office acoustics. Speaker phones may be wreaking havoc on office acoustics today, but the voice-activated computer will inevitably affect employee productivity drastically in ill-prepared open-plan offices in the future.

As offices strive to encourage teaming on the premise that “all of us together are more intelligent than any one of us individually,” says Koenig, neither can any one of these products or systems be aptly suited to do the job of all of them combined.

Jana J. Smith ([email protected]) is senior associate editor at Buildings magazine.

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