Placing sound masking on the front line of acoustic design

While acoustic professionals have always advocated the ABC Rule of absorbing, blocking, and covering unwanted noise, listing ‘C’ last reinforces the notion it is a final consideration and perpetuates the misplaced emphasis on isolation and absorption strategies when designing for speech privacy. Instead, the approach should be CAB: cover, absorb, block. By using sound masking to define and, therefore, know exactly what the background sound level will be anywhere in a facility, one can more accurately specify the remaining materials. Further, the volume can be increased at a later date if more acoustic control is needed or desired—a flexibility uniquely afforded by this technology.

Building professionals should not hesitate to take advantage of this value-engineering opportunity by employing a judicious balance of controlled minimum background sound and isolation in all facilities where speech privacy and noise control are priorities.

Photo © iStockphoto/BrianAJackson

Many people use the words ‘noise’ and ‘sound’ interchangeably. However, not all sound is noise. Rather, one can define ‘noise’ as any unwanted sound. Similarly, ‘silent’ and ‘quiet’ have different meanings. A silent space is one with no sound at all, whereas a quiet one has no unwanted sound.

Understanding these seemingly subtle differences is critical to comprehending the role sound itself plays in creating an effective acoustic environment. All too often, noise control strategies are mistakenly pursued with the intention of making a facility as silent as possible. However, the more silent one tries to make a space, the noisier it can seem to occupants. This phenomenon can be attributed to the fact an effective acoustic environment partially relies on an appropriate level of continuous background sound.

Due to improvements in construction materials, as well as quieter office and mechanical equipment, ambient levels in most facilities are already too low, leaving employees in library-like environments. These pin-drop conditions allow them to easily hear conversations occurring from a distance and even from within closed rooms. Though occupants typically describe such a workplace as ‘noisy,’ the root of the problem is they are, in fact, too silent. Put another way, the absence of sound makes noises easier to hear.

A sound masking system is the only acoustic treatment that can accurately control the background sound level within a facility. This technology basically consists of a series of loudspeakers installed above the ceiling or within an open ceiling, which distribute a sound most people compare to softly blowing air. The premise behind this solution is simple—any noises and conversations below the new background sound level are covered up, while the disruptive impact of those above it is lessened due to the reduction in the degree of change between the baseline and these volume spikes. Consequently, occupants perceive treated spaces as quieter.

There are many everyday examples of this effect, including running water, rustling leaves, or the murmur inside a busy restaurant. However, when introducing a sound to a workplace, it is vital to ensure it is also as unobtrusive as possible. While ‘white’ and ‘pink’ noise were utilized by early masking systems,* modern technologies are designed to produce a spectrum specifically engineered to balance acoustic control and occupant comfort. As no masking system can produce this spectrum ‘out of the box,’ post-installation tuning of the sound is an essential part of the commissioning process within each facility. If this step is skipped, the equipment is unlikely to provide the desired effects throughout the space.

* For more on the ‘colours’ of sound, see this author’s Construction Canada article at

Niklas Moeller is the vice-president of K.R. Moeller Associates Ltd., manufacturer of the LogiSon Acoustic Network sound masking system ( He has more than 25 years of experience in the sound masking field. Moeller also writes an acoustics blog at Moeller can be reached via e-mail at

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