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Acoustics First: Sound design as more than an afterthought

Photo © Jeffery Totaro. Photo courtesy CertainTeed

by Evan Troxel
Acoustics has an ever-increasing influence on modern commercial construction.  There are guidelines stating how loud classrooms should be, how much noise workers can be exposed to, and even the level of privacy needed in sensitive spaces. Innovative building products and technology can help professionals meet new and changing standards, but these tools are only as good as the designs they are incorporated into. (The author would like to thank James Johnson [Armstrong Flooring], Robert Marshall, P.Eng., BDS, LEED AP [CertainTeed Ceilings], and Lucas Hamilton [CertainTeed Gypsum] for their contributions to this article.)

The most important factor in acoustics management for commercial projects is including acoustics in the early stages of the building design. Too often, the effects of this factor on a space are treated as an afterthought and considered too late. It is absolutely critical for architects and designers to plan, test, and execute acoustic design strategies in every phase from flooring products to ceiling systems, and space design to furniture selection.

The best acoustic solution for any built environment begins with good design practices and informed product selections that have a direct impact on sound transmission and absorption.Careful consideration of the acoustic goals for the building is essential, and will lead to the construction of healthier, less-stressful spaces.

Back to the basics
Sound energy can be generated through the air or through the building structure. Many noise sources, such as loudspeakers placed in contact with the floor or the movement of heavy objects (e.g. carts, desks, and chairs) across a floor can cause vibrations producing both airborne and structure-borne acoustic concerns.

Sound energy interacts with the surrounding floor, walls, and ceiling (Figure 1). At each boundary, portions of the sound energy will be reflected back into the room, absorbed by the contacted surface, or transmitted through to adjacent spaces. Surface materials and room construction determine how the sound energy will spread.

Common noise sources in buildings—other than inhabitants—tend to relate to HVAC, plumbing, electrical systems, or exterior factors. Strategies for addressing these sources depend on the space category and specific uses. Private areas, such as classrooms and conference rooms, have different needs than public spaces like restaurants, lobbies, and clinics.

In these cases, noise criteria (NC), balanced noise criteria (NCB), and room criteria (RC) must all be addressed to limit background noise and create environments conducive to specific uses and needs (Figure 2).

Figure 1: The image at left shows the process of transmitting airborne vibration. The image at right depicts the process of transmitting structure-borne vibration.
Figure 2: Recommended background noise criteria for common spaces. For more information, consult the Springer Handbook of Acoustics, edited by Thomas Rossing and published in 2014.
Table © Springer Handbook of Acoustics
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