ACOUSTICS: The Sounds of Sustainable Design

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Dora Dorsey
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1 ACOUSTICS: The Sounds of Sustainable Design Allison McKenzie COURSE OUTLINE 1. Acoustical Impacts 2. The Acoustical ABCs 3. Design Best Practices 4. Sustainable Certifications Human comfort and productivity are very important aspects of sustainable design. Consequently, space acoustics are garnering growing attention in sustainable projects. This presentation will focus on three types of common environments where acoustics play a significant role: offices, classrooms and residential environments. 1. ACOUSTICAL IMPACTS: Different space types have different specific concerns, but acoustics have been shown to play an important role across typology. In Offices: proper acoustic design has been shown to improve focus by 48%, decrease error rates by 10% and decrease physical symptoms of stress by 27% i In Classrooms: learning environments with good acoustical characteristics have been shown to make learning deeper, more sustained and less fatiguing ii

This presentation will focus on three types of common environments where acoustics play a significant role: offices, classrooms and residential environments. 1.

2 In Residential Environments: lawsuits due to noise are the number 2 issue for litigation brought by owners and residents of condominiums, apartments and co ops iii, so good acoustic design can help decrease litigation and increase resident satisfaction. 2. THE ACOUSTICAL ABCs: ABSORPTION Used to control reverberation and echo Measured through a material s Noise Reduction Coefficient (NRC) and the resulting Reverberation Time (RT) BLOCKING Used to combat noise transfer between spaces Measured through Sound Transmission Class (STC) and Impact Insulation Class (IIC) COVERING Use of sound masking to cover other noises Measured through the decibel level of the masking sound NOISE REDUCTION COEFFICIENT (NRC): a representation of the amount of sound energy that is absorbed upon striking a specific surface. An NRC of 0 indicates perfect reflection and an NRC of 1 indicates perfect absorption. REVERBERATION TIME (RT): the period of time it takes for a sound event to become no longer audible. SOUND TRANSMISSION CLASS (STC): a rating of how well a building assembly attenuates (blocks) the transfer of airborne sound. A larger number means greater attenuation. IMPACT INSULATION CLASS (IIC): a rating of how well a building assembly attenuates impact sounds. A larger number means greater attenuation.

THE ACOUSTICAL ABCs: ABSORPTION Used to control reverberation and echo Measured through a material s Noise Reduction Coefficient (NRC) and the resulting Reverberation Time (RT) BLOCKING Used to

3 SOUND MASKING: The introduction of natural or artificial sound to cover up unwanted sounds. DECIBEL: A logarithmically defined unit of measure which expresses sound pressure level (roughly the loudness of a sound). Measured from 0 db to 140 db. BACKGROUND NOISE: Any sound other than primary, informational sounds. Background noise can be used as a masking device, but it can also be environmental noise that is problematic and distracting. 3. DESIGN BEST PRACTICES:

sound). Measured from 0 db to 140 db. BACKGROUND NOISE: Any sound other than primary, informational sounds.

4 C Strategies can be used separately or in conjunction to address all of the primary acoustical concerns of a space.

5 4. SUSTAINABLE CERTIFICATIONS: Many sustainable design certification systems now contain credits related to acoustic performance. Below is a summary of how acoustics can help you satisfy prerequisite and credit requirements in several versions of the LEED Rating Systems. LEED 2009 for Schools: This version of the LEED Rating System has an acoustics prerequisite that has limits for HVAC background noise and reverberation time. There is also a credit that lowers the acceptable HVAC background noise levels and adds STC requirements for interior and exterior walls. LEED 2009 for New Construction OR LEED 2009 for Commercial Interiors: The base rating system does not have any acoustics related prerequisites or credits. However, there are pilot credits for exterior noise control (New Construction only) as well as one that has reverberation time, STC requirements, and requirements for sound reinforcement and sound masking in certain situations. LEED v4 for Schools: The acoustics prerequisite in this version of the rating system are very similar to those contained in LEED 2009 for Schools, but it adds an exterior noise control requirement and lowers the allowable HVAC background noise decibel level. Similarly, the related credit also lowers the allowable HVAC background noise level. LEED v4 for New Construction OR LEED v4 for Commercial Interiors: There is a new credit for acoustic performance that limits HVAC background noise, sets STC requirements and reverberation time requirements and requires sound reinforcement and sound masking systems in certain situations. Allison McKenzie amckenzie@shp.com i David M. Sykes, Phd: Productivity: How Acoustics Affect Worker s Performance in Offices and Open Areas ii ANSI/ASA Standard S iii McGraw Hill Construction magazine, December 2005

LEED 2009 for Schools: This version of the LEED Rating System has an acoustics prerequisite that has limits for HVAC background noise and reverberation time.

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