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10/25/2012

Green Noise

Architects and interior designers don’t have to choose between sustainability, design and acoustic needs—now they can have all three.

By Kenneth P. Roy, PhD

 

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    Acoustical canopies can be used to reduce auditory distractions while adding visual interest to a space. View larger

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    Acoustical clouds can absorb sounds on both the front and the back, making them more effective than continuous ceilings. View larger

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    This chart summarizes the results of post-occupancy surveys on building IEQ conducted by the CBE across both unrated and LEED-rated buildings in the United States. Acoustic Quality is the lowest performing IEQ factor in both sets of data, and is the only negative (dissatisfaction) factor overall. View larger

educational acoustics
Considering that the primary mode of teaching involves speech and listening, the quality of the acoustic environment in a classroom is crucial. LEED for Schools recognized the unique nature of the design and use of K-12 schools, and was the first of the U.S. Green Building Council (USGBC) rating systems to include acoustics as an integral and important element of IEQ.

To provide classrooms that enhance learning, LEED for Schools includes a minimum acoustical performance prerequisite. To meet it, two requirements must be achieved:

  1. Classrooms and other core learning spaces must include sufficient sound-absorptive finishes to comply with a maximum reverberation time of 0.60 seconds (classrooms less than 20,000 cubic feet).
  2. Classrooms and other core learning spaces must meet a maximum background noise level from HVAC systems of 45 decibels A-weighted (dBA).

Compliance with the first requirement is accomplished in one of two ways:

  1. By confirming that 100 percent of all ceiling areas (excluding lights, diffusers and grilles) are finished with a material that has a NRC of 0.70 or higher.
  2. By confirming that the total area of acoustical wall panels, ceiling finishes and other sound-absorbent finishes equals or exceeds the total ceiling area of the room (excluding lights, diffusers and grilles). All materials in the calculation must have an NRC of 0.70 or higher.

The proper use of sound-absorbing materials will significantly reduce reverberation, however, the location of acoustic treatments is a vital consideration. In classrooms where there is no fixed position for the teacher and ceiling heights are about 10 feet, the best and most cost-effective option is to place most, if not all, of the sound-absorbing material on the ceiling, in the form of a suspended acoustical ceiling.

If ceiling heights are greater than 12 feet, an increasing amount of sound-absorbing material should be placed on the walls. If there is no possibility for wall treatment, consider placing three-dimensional furnishings such as bookshelves along the walls to ensure sound waves are scattered, thereby reducing the possibility of distant echoes.

 

Kenneth P. Roy, Ph.D., FASA, is a senior principal research scientist for acoustic technologies for Armstrong Building Products in Lancaster, Pa. He can be reached at kproy@armstrong.com.

 


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