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Part 1: LEED v4 Offers More Stringent Acoustical Standards
By Daniel Overbey
April 2014 -
Typically, the term indoor environmental quality (IEQ) evokes considerations of healthy indoor air along with visual and thermal comfort. Adequate ventilation, indoor pollution source control, equitable controllability of lighting systems, and access to daylight and views appropriately draw focus as key concepts for design teams endeavoring for optimal indoor environments. However, the high-performance design community is now beginning to recognize the importance of acoustical comfort as an important sensory influence in assessing IEQ. As part of that recognition, the new LEED v4 offers more stringent acoustical standards.
Loud sounds and ambient environmental noise can be detrimental to the experience of a space, but recent research is going beyond anecdotal evidence to prove just how vital acoustical performance can be for the success of a project — especially schools and healthcare facilities.
When noise levels in a classroom are too high, students and teachers lose the ability to intelligibly understand each other. According to the United States General Accounting Office (GAO), more than 28 percent of elementary and secondary schools exhibit unsatisfactory environmental noise conditions. In a GAO study of 21,900 schools, concern over acoustics was rated higher than ventilation (27.1 percent), physical security (24.2 percent), indoor air quality (19.2 percent), heating (18.9 percent), or lighting (15.6 percent).
The detrimental effects of poor acoustical environments spread beyond learning environments. Another study, published in the British Journal of Psychology, asked workers to perform two tasks: 1) memorize and then recall a piece of prose; 2) undertake simple mental arithmetic. During the test period, workers were subjected to recordings of general office noise. The research found that the accuracy of the subjects' work was reduced by approximately 67 percent when exposed to the recorded office. A later study found that 57 percent of workers in an office environment have their concentration negatively affected by nearby sounds and background noise.
Beyond annoyance or decreased productivity, the effect of poor acoustical environments may also impact health.
Recently, the World Health Organization (WHO) examined evidence from large-scale epidemiological studies linking the population's exposure to environmental noise with adverse health effects and established a link between road traffic noise and increased risk of cardiovascular diseases, including myocardial infarction. In fact, an emerging body of work is beginning to establish a link between exposures to environmental noise and sleep disturbance, cognitive impairment in children, and Tinnitus, among other human health concerns. A facility's acoustic performance matters for reasons of comfort, occupant performance, and human health.
Acoustics have been a niche concern for so long that many are uncomfortable with the topic. The following considerations will help achieve good acoustic performance:
Engage an expert: An acoustician can prove very helpful in achieving specific acoustic performance criteria. Alternatively, a mechanical engineer with a specialized knowledge in acoustics can be effective. This acoustic expert should work with the project team to help conduct a site analysis, implement strategies, perform calculations, and take field measurements.
Identify referenced standards: LEED v4 permits a reasonable degree of flexibility within the acoustic performance credit framework. Referenced standards can be bypassed in lieu of local equivalents. Teams should determine the appropriate standards early in a project and commit to them.
Define the criteria early: Teams will be most successful if acoustics are planned for early in the design process. Different user groups have unique requirements that need to be carefully documented. Teams should match appropriate strategies to specific criteria.
HVAC background noise: Determine specific acoustic and HVAC needs, then assign and coordinate design and performance criteria. This will affect what mechanical equipment is selected.
Sound isolation: Complete the calculations during the design phase. Identify or calculate STCc ratings for all assemblies. Verify calculations after substantial completion of construction. Measure the Noise Isolation Class (NIC) for all assemblies.
Reverberation time: A metric heavily influenced by design specifications, criteria should be identified and coordinated. The entire team should have a general understanding of spaces with sensitive or otherwise atypical reverberation time requirements.
Acoustics: LEED v4 Tunes Up Acoustic Performance
Part 2: LEED v4 Tackles Acoustics With New Noise Control Pilot Credit, Expanded Acoustic Performance Credits
Part 3: LEED v4 Expands Acoustic Performance In Multiple Areas