Sound masking for open office environments

by Michael Arny, P.E., LEED AP, and Mary Reames, J.D., LEED AP, Leonardo Academy — In open office environments, the noise from co-workers and office equipment can be distracting. Privacy can also be an issue, particularly in financial and health care service organization environments.

Facility managers may get complaints about noise levels in open office spaces. One of the solutions that can be considered is the installation of a sound masking system. This article gives you an introduction to sound masking systems.

How Sound Masking Works

Office spaces may be either too quiet or too loud. In offices that are too quiet, there is a wide dynamic range between the generally quiet environment and the occasional loud sound in the office. This makes loud sounds really stand out, like the proverbial pin dropping in a library. In offices that are too loud, conversations and equipment noise reduce employees’ ability to concentrate. Both situations create less-than-ideal work environments.

It is not practical to absorb or block all the sound around us because some will be reflected over and around partitions or travel through penetrations in walls or ceilings. This sound that is not practical to absorb or block can be masked by adding selected sound to the office space.

Purposefully adding sound into an open office environment lets you control the sound levels overall; a sound masking system creates a uniform ambient noise so there is a narrow dynamic range between the loudest sounds and the background noise level in the office. This will help you improve the functioning acoustics of a space so co-workers can better concentrate without distraction. The sound that masking systems deliver should be barely perceptible, but will often be enough to cover other, distracting noises.

Masking systems can also specifically target and mask voices. The frequency range of human speech is 80 to 1,100 Hertz. Adding a uniform background sound in this frequency range makes conversations that are more than a short distance away hard to understand, thus providing privacy for the conversation’s participants.

Sound masking differs from “white noise” because it targets the specific spectrum of conversation. Whereas white noise is audible and may be distracting in its own right, such as a noisy HVAC system or a fan, a properly engineered sound masking system should not be noticeable but will make other noises, such as other people’s conversations, harder to hear.

Sound masking is also not the same as noise cancellation. True noise cancellation works to cancel a sound pressure wave by creating an opposing wave; it works best in small, controlled environments with known noises, such as engine noise in the cab of a semi. Sound masking is less precise, and therefore more appropriate for larger, less controlled environments such as offices.

Metrics for Sound Masking Achievements

ASTM has developed a testing method for assessing speech privacy, called the Standard Test Method for Objective Measurement of Speech Privacy in Open Offices Using Articulation Index (ASTM E1130-16). This test can be used to measure current levels of speech privacy and to evaluate the effectiveness of a sound masking system. It measures the ability to hear conversations spoken in a normal male voice on a spectrum (the Articulation Index) from 0.0 (unintelligible) to 1.0 (understood).

Exploring the Installation of a Sound Masking System

Before you consider sound masking, here are some preliminary questions to answer:

  • Can the noise problem be addressed by moving or adding sound barriers, such as cubicle partitions?
  • Can the noise problem be addressed by introducing workplace noise policies or other cultural adaptations?

If you decide to further explore a sound masking system, here are some questions to ask:

  • Where is it needed, and how much floor area should be covered?
  • Where are speakers located – above ceiling tiles or below?
  • How many speakers are needed?
  • How are the system and the speakers controlled?
  • How easy is it to make system adjustments?
  • Where are controls located?
  • What does it cost?

In the right setting, a sound masking system can be truly effective at improving the work environment, increasing productivity, and keeping employees happy.

Leonardo Academy is a nonprofit organization that develops sustainability solutions through consultation and certification services in the LEED Green Building Rating System and the Cleaner & Greener sustainable event program. Leonardo Academy also provides sustainability and continuing education training, including training for the LEED Green Associate credential for individuals who support green buildings in their profession, such as building owners and facility managers.

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