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Sound Control Design & Materials for Sound Transmission Through Building Walls InspectAPedia®  -     What is the definition of STC Sound Transmission Class? Table of Sound Transmission Class Ratings - (STC ratings) for various building wall & floor designs Sound transmission control design details for building walls and partitions

Here we define STC - sound transmission class and we provide a table of design details that show STC rating for various building wall framing designs. Sound transmission reduction wall designs are given for goth single stud and staggered double stud structural and partition walls. We include soundproofing suggestions for high noise level areas such as music rooms as well as areas where privacy is a concern such as in counseling and psychotherapy offices. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons. The page top table from the above text shows sound transmission class ratings mapped against typical sound levels in buildings.

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Sound Transmission Class: What are STC Ratings

How effectively a wall or floor reduces airborne sound is measured by STC ratings (sound transmission class). Roughly speaking, the STC rating equals the reduction in decibel levels across the partition.

So, for example, a 50 dB noise on the other side of an STC 35 wall will sound like a 15 dB noise to the average listener (see our Table of STC ratings and noise reduction left).

Walls and floors in the field often measure lower than in laboratory ratings due to variations in workmanship as well as leaks and bypasses.

The higher the STC rating, the more likely it is to be compromised by site conditions. For that reason, it is best to select a building assembly rated at least 5 points above the design goal.

Sound Control Design & Materials for Sound Transmission Through Building Walls

Sound transmission reduction In single-stud walls, the most cost-effective sound control upgrade is to double the drywall on one side and add insulation to the cavity, increasing the sound transmission class (STC) from 33 to 40 (see Table of STC ratings of typical wall assemblies at left - click to enlarge the table). The joints on the second layer of drywall should not line up with the first layer. Double-framed soundproof wall construction details: To achieve substantially higher STC ratings requires adding a resilient channel to one side of the wall or decoupling the two sides of a wall with double framing. With no rigid connection bridging the two sides of the wall, sound transmission is significantly reduced. Decoupling and also increasing mass, such as doubling the drywall layers, will help cut transmission of low-frequency sounds as well. For party walls between adjacent living units, STC ratings should be a minimum of 50. Recommended STC levels between bedrooms and adjacent rooms in single family homes and apartments are shown in our Table of Recommended Sound Control for Bedroom Partitions in Single-Family Dwellings. Where privacy and quiet are of concern to clients, a minimum STC rating of 45 is a reasonable target for bedroom and bathroom partitions. For higher STC wall sound transmission values required for special situations, such as a music room or home office, additional upgrades include increasing the mass on either side of the cavity, enlarging the cavity, or adding fiberglass batts or other sound-absorbing materials. Filling the gap more than three quarters of its width with insulation provides little additional benefit. In fact, stuffing the cavity too tightly could reduce the benefit of the fibrous insulation by creating a solid bridge. In general, polystyrene and other closed-cell insulations are poor sound absorbers and provide little benefit. Closets along a wall can help buffer sounds as long as doors are solid, not louvered.

-- Adapted with permission from Best Practices Guide to Residential Construction.

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• Daniel Friedman - principal author/editor of the InspectAPedia^® Website
• Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
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SOUND CONTROL in BUILDINGS
  ACOUSTICAL SEALANTS
  Principles of Sound Transmission
  How Sound Levels are Measured
  Sound Absorption vs. Sound Isolation
  Sound Isolation Strategies
  Cut Off Flanking Sound Paths
  Sound Transmission Class Ratings
  Sound Control for Walls
  Sound Control for Floors
  Sound Control for Plumbing
  Properties of Soundproofing Materials
  Acoustical Sealant for Sound Control
  Resilient Channel for Sound Reduction
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  Duct Insulation for Soundproofing
  White Noise & Sound Conditioners
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VENTILATION in BUILDINGS
WATER ENTRY in BUILDINGS
WINTERIZE A BUILDING
WOOD Burning Heaters Fireplaces Stoves

• Marpac, produces white sound generators, a product that they identify as the Marpac sound conditioner. Marpac can be contacted at http://www.marpac.com/ or contact the Marpac Corporation, P.O. Box 560 Rocky Point, NC 28457 Phone: 800-999-6962 (USA and Canada) Fax: 910-602-1435 1-910-602-1421 (worldwide), 800-999- or email: info@marpac.com
• Sound Oasis sound conditioners are produced by Sound Oasis: http://www.sound-oasis.com/ email: info@sound-oasis.com or 1-866-625-3218

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• Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Wiley.com and also at Amazon.com. See our book review of this publication.

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