Machinery Noise Control

Common building equipment can make noise or vibration, and adversely affect the use of indoor and outdoor space.  A few selected examples include:  pumps, fans, cooling towers, blowers, chillers, compressors, generators, and electrical transformers.

Vibration is important too.  Any rotating or reciprocating equipment has the potential to cause noise problems indoors, by transmitting vibration into the structure.  That vibration can travel throughout the building and radiate sound, often in distant locations.

Noise control involves the proper application of enclosures, mufflers, absorptive lining, silencers, vibration isolation, and similar measures.  Space planning is another useful technique.  Buffer spaces placed between noisy equipment and noise-sensitive users can save a great deal of effort and expense on noise control.  Storage space, copy rooms, or corridors can be used to separate the mechanical room from offices.

Heating, ventilation and air conditioning (HVAC) equipment must deliver fresh heated or chilled air constantly, but background noise must remain within a reasonable range of noise levels.  These noise levels are expressed as the Noise Criteria (NC).  NC values are used to describe continuous background noise, and accounts for human sensitivity to low, middle and high frequency sounds.

Equipment noise can be a community noise issue too.  Exhaust fans or rooftop refrigeration equipment may create noise that offends nearby neighbors.  Large electrical transformers sometimes create an annoying "hum", which can be audible from great distances.  Equipment may even be noisy enough to violate local noise ordinances, especially at night when the limits are often stricter.

All of these factors should be considered during the design of a project.  The goal is to avoid creating a noise problem that will be expensive and difficult  -- or sometimes even impossible -- to solve later.