sound masking

How to maintain sound masking performance

Don’t just set and forget systems used for speech privacy, noise control
Thursday, December 6, 2018
By Niklas Moeller

Open-plan space, modular walls, and reflective surfaces such as glass, concrete, and metal are just a few of the design trends making today’s interiors even more dependent on sound masking for speech privacy and noise control. Ensuring this technology continues to function as expected over the course of its life cycle not only involves maintaining the health of the equipment used to generate and broadcast the sound, but also the efficacy of the sound itself.

The system

The components used by modern sound masking systems require little preventative maintenance. In fact, some networked technologies are able to actively monitor for various types of issues and use an alarm (visual or audible) or email to alert the client to a service requirement. If the system does not provide this feature, it is prudent to check the following equipment on a routine basis (e.g. annual), when work is done within the ceiling space, or if an occupant reports a problem:

Power

Most systems use low-voltage DC power supplies. While those of high quality typically last many years, they can eventually fail. Occupants will likely notice a power failure, but it is wise to periodically verify operation. Some sound masking systems offer fail-safe power supplies; in other words, if a power supply fails, a second one takes over to ensure continuous operation of the system.

Cabling

Work done on other elements within the ceiling can inadvertently cause damage to the sound masking system’s cabling or result in the disconnection of its components.

Loudspeakers

Loudspeakers are installed in a grid-like pattern within the ceiling space and deliver the sound, as well as paging and music signals if the system has such capabilities. Some systems continuously monitor loudspeaker performance, eliminating the need to manually enter the ceiling to check each loudspeaker.

At this time, also take the opportunity to review and adjust customized settings related to various ancillary components and functions, such as:

Programmable keypads

Keypads allow occupants of private offices and meeting rooms to modify masking and paging volumes, as well as paging channel selection, as needed (e.g. to accommodate videoconferencing). Their zoning, functions and volume limits should be checked and changed, if desired.

Paging and music

Most sound masking systems also provide overhead paging and background music functions. Zones and volumes should be altered, as needed.

Timer

Some systems allow a schedule to be established that adjusts the masking level to suit expected occupation densities throughout the day, week or year. For example, security personnel might want the volume to lower during the night so that they can hear any disturbances. Zones, scheduling and exception dates (e.g. holidays) should be reviewed and updated to reflected changing requirements.

Security

Some systems provide various levels of password-protected access to the system’s features and settings, depending on an individual’s role. Permissions should be reviewed to ensure they still meet the organization’s needs.

In certain cases, the system’s design might need to be physically modified; for example, when newly constructed walls cross existing zones or major changes are made to ceiling treatments. In this case, contact the vendor so that they can review loudspeaker placement and zoning.

The sound

When properly implemented, a sound masking system is a highly effective contributor to the overall acoustic performance of open plan areas, as well as to the speech privacy levels experienced in closed rooms. However, the system cannot achieve these goals from the moment it is powered on. Regardless of its design or the position of its loudspeakers, the sound it emits interacts with the facility’s layout, finishes and furnishings.

In order to deliver the expected value rather than simply introducing a background noise to the facility, the vendor’s technician or an acoustician must tune the sound to meet a specific masking spectrum or ‘curve.’ This goal should be set by a third party such as the National Research Council (NRC) or an acoustician, rather than by the system’s manufacturer or vendor. The typical range is between 100 to 5,000 hertz (Hz), but it can go as high as 10,000 Hz.

The exact tuning method varies by product, but generally speaking, the technician uses a sound level meter to measure the sound at ear height (i.e. the level at which occupants experience the masking effect), analyzes the results, and adjusts the volume and frequency settings accordingly. They repeat these steps until the curve is met at each tuning location. System designs with small zones (e.g. of one to three loudspeakers) offer the technician more test and adjustment points, allowing them to more accurately achieve the specified spectrum throughout the installation. The more precisely and consistently the curve is met, the better the outcome.

A good guideline is to require a test in each 1,000-square-foot (90-square-metre) open area, as well as within each closed room. Some systems can adjust for smaller areas, but this is an acceptable baseline. Overall volume is typically set to between 40 and 48 A-weighted decibels (dBA), and the results should be consistent within 0.5 dBA. Frequency should also be measured. It’s reasonable to expect a variation of plus or minus two decibels in each third-octave band. At the conclusion of the tuning process, the vendor should provide a written report of the results.

If changes are made to the space (e.g. to furnishings, partitions, ceiling, flooring) or to its occupancy (e.g. relocating call centre functions to an area formerly occupied by accounting staff) in the future, the technician should return to measure the sound and adjust the settings in zones where it no longer meets the specified masking curve or the client’s needs. It is not advisable for clients to handle these changes themselves because specialized training and equipment are needed to ensure they are properly made, measured and documented.

The likelihood that changes will occur during a sound masking system’s 10- to 20-year lifespan is almost certain. Therefore, organizations simply cannot take a ‘set-it-and-forget-it’ approach when it comes to the equipment or the sound it delivers within their space.

Niklas Moeller is the vice president of K.R. Moeller Associates, manufacturer of the LogiSon Acoustic Network and MODIO Guestroom Acoustic Control. He has more than 25 years of experience in the sound masking field.

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