Better Late Than Never: Retrofitting sound-masking to improve acoustics

Photos © Zahid Ghafoor. Photos courtesy K.R. Moeller Associates Ltd.
Photos © Zahid Ghafoor. Photos courtesy K.R. Moeller Associates Ltd.

By Niklas Moeller, MBA
It is an all-too-common scenario—a company moves its employees into a highly anticipated new facility only to be met with complaints regarding speech privacy and noise levels. Perhaps the building’s acoustic performance was not adequately planned before construction, or consequences of various interior decisions were not understood. Regardless, the poor results are undeniable and, unfortunately, familiar.
In the last decade, sustainable, flexible, and collaborative design trends have systematically eliminated many methods of controlling acoustics. The percentage of open-plan space has grown and so have occupant densities. At the same time, partitions have lowered or disappeared altogether, and the use of absorptive finishes has diminished, allowing noises to travel further and last longer.

Closed rooms are increasingly built using:

  • glass walls;
  • walls stopping at the suspended ceiling;
  • demountable partitions; and
  • sliding doors.

While these choices may have some esthetic appeal and help meet particular objectives or short-term budget goals, they have also diminished the acoustic performance of many workplaces by reducing room-to-room isolation.
The work environment sets the stage for employee performance and plays a role in absenteeism and retention rates. Therefore, investing in solutions for this type of ‘facility malfunction’ is easily justified.

According to the 1998–2008 BOSTI Associates study, “Disproving Widespread Myths About Workplace Design,” employees typically account for about 82 per cent of a company’s primary costs, over the 10-year period of the study. This amounts to more than a building, its operations and technology combined; employees are an organization’s biggest expense, and also its greatest asset. Effective acoustics are essential to providing speech privacy and freedom from distracting noises, as well as enabling employees to work normally without disrupting others.

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To create this type of environment, acoustic professionals apply techniques to absorb, block, and cover noise (i.e. the ABC rule) (For more, see the article, “The Green Soundscape” by Niklas Moeller, in the July 2010 issue of Construction Canada). Each of these strategies contributes differently to overall acoustic performance. Consequently, when problems in an existing facility are encountered, the source is usually in the omission of one of the methods mentioned, or imbalanced application within the space.

In the last decade, many methods of controlling acoustics have been systematically eliminated. The percentage of open-plan spaces has increased, partitions have lowered or disappeared, absorptive finishes have been replaced by hard surfaces, and floor plates have narrowed. Photo © iStockphoto/Goran Bogicevic
In the last decade, many methods of controlling acoustics have been systematically eliminated. The percentage of open-plan spaces has increased, partitions have lowered or disappeared, absorptive finishes have been replaced by hard surfaces, and floor plates have narrowed.
Photo © iStockphoto/Goran Bogicevic

At this point, the organization must determine:

  • which acoustical treatments are capable of addressing the issues;
  • budget available for solutions; and
  • degree of operational disruption the workplace can weather during their implementation.

The answers to these questions largely determine the course of action. It often comes down to which treatment offers the greatest opportunity for improvement, with minimal upheaval.

The missing element
Due to advances in construction materials and mechanical systems, modern facilities are often missing an appropriate ambient (or background) sound level, which would serve to cover conversations and noise. Today, ambient levels are typically in the mid-30 to low-40 decibel range. Levels are even lower in buildings using alternative ‘green’ HVAC systems and facilities with underfloor air distribution (UFAD) systems because they lack the traditional noise created by forced air ventilation. This ‘pin-drop’ environment allows noise and conversation to be easily heard, even from a great distance. Further, the background sound present does not exhibit the correct mix of frequencies needed for speech privacy, noise control, and comfort.

The lack of adequate background sound can be addressed using a sound-masking system. This technology consists of a series of loudspeakers installed in a grid-like pattern in the ceiling, as well as a method of controlling zoning and output. The loudspeakers distribute a comfortable, engineered sound, maintaining the facility’s ambient level at an appropriate and consistent volume. Though the sound is similar to softly blowing air, it is specifically designed to mask speech frequencies. It also covers up unwanted noises or reduces impact on occupants by decreasing the magnitude of change between baseline and peak volumes in the space.

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