Today's office environments have several shared characteristics:

In an effort to cut back on real estate cost and wasted workspace, many companies are opting for open offices.

To increase employee interaction, upper management frequently abandons private office space to join the open office plan.

An increase in team projects and an emphasis on collaboration requires more group work and shared working space.

While office walls tumble, technologies such as speakerphone and interactive Internet meetings are still popular.

Equipment noise is difficult to avoid in an open office setting.

Although the office of today is geared towards cost saving, an open workspace creates the unique problem of distractions from excessive noise. Numerous studies convincingly demonstrate that noise is the number one contributor to lack of productivity in the workplace. It is difficult, if not impossible, to pay attention to details while distracting noises are prevalent.

Increased interests in the health, safety, comfort and productivity of employees gave birth to the ergonomics boom. Acoustical concerns in the workplace parallel, and far exceed, the trend in ergonomics.

One way to create an atmosphere that meets the needs of both the employer and employee is to install a sound masking system. Currently, 15% of new office buildings are equipped with masking systems and the trend is expected to continue and expand over the next few years.

How Masking Systems Work
Masking systems provide ambient background sound that reduces exposure to distracting office noises by emitting a discreet, electronically-generated sound through specially installed, unobtrusive speakers. When installed properly, employees won't be aware of the pink noise being generated around them, but they will be able to focus on their work without unwanted sound distractions. Of course, carefully choosing office furniture, wall treatments and flooring systems will also contribute to a productive work area.

Checklist of Masking Systems for Open Plans
Ideally, speakers should be in enclosures located just above suspended ceilings, aimed upward toward hard plenum surfaces. If sound absorbing insulation is applied to the underside of the structural deck, speakers should be aimed downward (or possibly sideways) or speaker enclosures that reflect sound downward should be used.

Plenums should have uncomplicated air duct layouts and smooth sound-reflecting structural surfaces to allow wider spacings between loudspeakers.

Coverage should include adjacent areas (or zones) so occupants moving about the building will not notice the masking system.

Masking should not exceed a sound level of 45 to 50 dBA because occupants tend to raise voices to compensate, thus defeating the intended masking effects. Occupants may also begin to complain about the sound level when it exceeds 50 dBA.

To reduce the likelihood that occupants will notice background masking, consider installation procedures that initially operate the system at low sound levels. Then gradually increase the level by about 1 dB each day until the desired masking level is achieved in a week to ten days or longer.

A well-designed masking system deliberately garbles the sound it produces and therefore should not be used for paging and routine office functions.

Provisions can be made to reduce masking noise levels during off-hours to enhance ability of security personnel to hear unusual sounds.

Be sure to consider the consequences of background masking on the usability of open plans by hearing-impaired persons. For example, when background noise levels exceed 30 dBA, hearing-impaired persons (even when using hearing aids) have far more difficulty understanding speech than do normal-hearing persons.

In addition to avoiding excessive noise levels, background noise from electronic sound masking systems in open office plans should have a neutral tonal quality. This may be facilitated by designing the system to simulate familiar building sounds, such as the airflow at diffusers and registers of HVAC systems. The electronically produced sound levels in the finished room should be no higher than necessary to mask unwanted intruding speech and so that pronounced hisses are avoided. The sound level of the masking system should be neither too high nor too low, and the spectrum should roll off at the high end of the frequency range.

In open plans, loudspeakers can usually be hidden in plenums above suspended ceilings. This strategy can achieve uniform masking sound throughout the room. Be careful when designing this kind of installation because openings for return or supply air in ceilings and luminaries can be noticeable sound leaks, which make it difficult to achieve uniform masking sound.

For preliminary planning, loudspeaker spacing, S, can be found by:

              S = 1.4 (2D + H - 4)

Where S = spacing between loudspeakers (ft)
              D = plenum depths (ft)
              H = floor-to-ceiling height (ft)

Closer spacings may be required when spray-on, sound absorbing fire protection or insulation is applied to the underside of structural decks, or when complicated air duct layouts or deep structural members obstruct plenums.