Building Acoustics and Noise Control Services
From Building Sciences
The combined effects of three areas of design affect the acoustic environment of a space:
- architectural noise control (the separation of noisy areas from quiet areas);
- mechanical noise control (noise produced by equipment such as HVAC); and,
- room acoustics (the way that noise produced within a space sounds to listeners within that same space).
Producing the appropriate acoustic environment for a space requires the appropriate corresponding noise control design in each of these three categories.
Architectural Noise Control
Architectural noise control addresses the acoustic separations between spaces, which primarily includes partitions, floors, and ceilings. However, the performance of a separation is only as good as its weakest point, and therefore, particular attention must be paid to minimize the effect of weak spots and flanking paths in details such as glazing; doors; HVAC, electrical, and plumbing penetrations; electrical boxes; and intersections of walls, floors, and ceilings. It is therefore necessary to ensure that the appropriate specifications are clearly incorporated in the architectural drawings, and that thorough site inspections are conducted to verify that these details have been correctly included in the construction.
Mechanical Noise Control
Mechanical noise control includes vibration control of equipment, and reduction of airborne noise as it passes through ducts and other pathways. Achieving the appropriate background noise is critical to proper enjoyment of the space. For example, an open office requires background noise that must not be too loud as to be distracting while providing sufficient masking of conversations and other noises. On the other hand, a meeting room must have a low background noise to allow for clear speech intelligibility. The characteristic of the noise is also critical; a broadband noise at an appropriate level will be unnoticeable and provide sound masking, whereas a tonal hum at the same noise level will be distracting and annoying. Mechanical noise control design considers the level and type of noise produced by the mechanical equipment, numerically models the noise travelling through various pathways (such as ducts), and selects the appropriate noise control products to achieve the background noise level appropriate for the space.
Room acoustics deals with the way sound interacts with the room, specifically, the way it is reflected or absorbed by surfaces within the room. A reverberant room provides many reflections for sound such that the sound stays in the room long after it was produced. A “dead” room provides very few reflections as surfaces will instead absorb the sound so the sound disappears shortly after it is produced. A reverberant room can appear loud even if it is not (such as an empty warehouse), and a “dead” room can appear quiet even if it is not (such as a clothing store). One of the more critical aspects of room acoustic design is its effect on speech intelligibility. Early reflections, reflected sound that reaches the listener soon after the direct sound, can complement the direct sound and increase speech intelligibility, particularly at a distance. On the other hand, late reflections, reflected sound that reaches the listener long after the direct sound, will interfere with the direct sound and decrease speech intelligibility. Room acoustic design considers the use of the space, the size of the space, and the selection of the appropriate absorptive (or reflective) finishes to achieve the desired acoustic environment.