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Sound Control in Buildings - Cut off Flanking Sound Paths InspectAPedia®  -     What are flanking pathways for sound leakage in buildings How do we cut off flanking paths for sound Design details for soundproof doors and doorways Use of sound sealants for partition walls Controlling transmission of bathroom noises in buildings How to make a building quiet: sound isolation strategies

This article explains how sound flanking paths, sound leaks around and through building components, defeats incomplete attempts to reduce building sound transmission and noise levels. We include design details for sound reducing details in buildings including soundproof office doorways and doors. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons. The page top photograph shows a pair of solid core doors installed at the entry to an office where sound transmission and privacy are a concern. Below we provide more details about soundproofing at doorways.

© Copyright 2009 Daniel Friedman, Steve Bliss, Wiley & Sons, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

How to Cut Off Flanking Paths for Sound

Continuing from from Best Practices Guide to Residential Construction:

Sound takes the path of least resistance between rooms, through any air leaks or through rigid connections in the structure itself. These routes that bypass efforts at sound insulation are called flanking paths. These can significantly reduce the effectiveness of soundproofing efforts. Building walls with high STC ratings will do little good if sound can pass easily though electrical outlets or a thin, loosely fitting door.

For example, an ungasketed door or the equivalent of a one-inch-square hole in a wall can reduce an STC 50 wall to STC 30. Common flanking paths include:

• Air leakage around partitions; around doors; and through plumbing penetrations, back-to-back medicine cabinets, unsealed electrical outlets or recessed lights (Figure at left).
• Shared ductwork between two rooms.
• Hollow-core doors and single-pane glass, which are good sound transmitters.
• With resilient channels, a few drywall screws that penetrate into the ceiling joists, undermining the decoupling system.
• With decoupled framing, a solid path through a band joist or drywall panel that provides a bypass for structure-borne sound.

Minimizing sound noise transmission flanking paths requires both good planning and workmanship. Common strategies to control flanking path for noise in buildings include:

• Avoid back-to-back holes for electrical and mechanical equipment.
• Partition wall sealants: Along partition bottoms, leave a 1/4-inch gap between the drywall and subfloor, and fill with acoustical sealant.
• Bathroom noises: On bathroom partitions, install drywall all the way to the floor before installing the tub and seal all plumbing penetrations through walls with a flexible sealant.

Design Details for Soundproof Doors & Doorways

• Soundproof doorways: Upgrade to solid-core doors and add weather-stripping. Our photo (left) shows an installation of doubled solid core doors that has been found effective in minimizing sound transmission between a counseling office and its waiting room. Similar to the double sound-transmission resistant doorway shown at the top of this page, here the designer incorporated a short hallway between a waiting room and the counseling office. Outside a waiting room closet, forming one wall of the entry hall, provides additional soundproofing and privacy for this space. As we discuss below at Sound Control for Walls, closets provide additional sound transmission buffering provided their doors are solid, not louvered.

Addressing obvious flanking paths is often the most cost- effective step in soundproofing a home. Strategies such as sealing air leaks between rooms, upgrading doors, and adding weather-stripping may provide adequate sound isolation without the need for more exotic and expensive measures.

In general, sound-resistant doors should be within 10 Sound Transmission Class (STC) points of the surrounding wall. Solid-core doors are recommended for bedrooms and bathrooms.

Where higher-level sound isolation is required, you will need to add high-quality gasket-type weather-stripping and a sealed threshold. Also the gap between the door jamb and studs should be caulked or grouted to avoid sound leaks around the door. A doubled sound transmission resistant interior door installation is shown at Cut Off Flanking Sound Paths.

For even higher ratings, which might be needed for a music room, for example, double doors are required (see our Table of Sound Transmission Characteristics of Interior Doors).

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

Continue reading about methods for sound control in buildings by using the links provided just below.

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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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INTERIORS of BUILDINGS
AGE of a BUILDING - how to determine
AIR BYPASS LEAKS
AIR LEAK DETECTION TOOLS
AIR LEAK MINIMIZATION
AIR SEALING STRATEGIES
ANIMAL ALLERGENS
ASBESTOS IDENTIFICATION IN BUILDINGS
ATTIC LEAKS, CONDENSATION & ATTIC MOLD
BATHROOM VENTILATION
BASEMENT HEAT LOSS
BASEMENT LEAKS Moisture or Mold
BLOWER DOORS & AIR INFILTRATION
CHIMNEY INSPECTION DIAGNOSIS & REPAIR
COMBUSTION AIR for TIGHT BUILDINGS
CRAWL SPACES
ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR
ENERGY SAVINGS in BUILDINGS
ENVIRONMENTAL HAZARDS
FIREPLACE Damage & Unsafe Hearths - Settlement
FLAT ROOF MOISTURE & CONDENSATION
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOORING TYPES & DEFECTS
FREEZE-PROOF A BUILDING
HEAT LOSS in BUILDINGS
HEAT LOSS DETECTION TOOLS
HEAT LOSS INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HOUSEWRAP AIR & VAPOR BARRIERS
HUMIDITY LEVEL TARGET
ICE DAM PREVENTION
INSULATION IDENTIFICATION GUIDE
INSULATION LOCATION for BASEMENTS
INSULATION LOCATION for CAPES, CRAWLSPACES
INSULATION R-Values & Properties
INSULATION & VENTILATION INSPECTION & IMPROVEMENT
INSULATION LOCATION for BASEMENTS
INSULATION LOCATION for CAPES, CRAWLSPACES
INSULATION for GREENHOUSE or SOLARIUM
INSULATION MATERIAL IDENTIFICATION GUIDE
INSULATION R-Values & Properties
Insulation Values of Log Home Walls
LOG HOME GUIDE
MOBILE HOME INSPECTIONS
MOLD INFORMATION CENTER
ODORS & SMELLS DIAGNOSIS & CURE
PAINT FALURE, DIAGNOSIS, CURE, PREVENTION
PLASTER & BEAVERBOARD & DRYWALL
ROT, FUNGUS, TERMITES
  TERMITE SHIELDS vs TERMITICIDE
ROT, TIMBER FRAME
SEARS KIT HOUSES
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
  Insulation Details for Sound Reduction
  Gasketing for Noise Control
  Duct Insulation for Soundproofing
  White Noise & Sound Conditioners
STAIN DIAGNOSIS
STAIRS, RAILINGS, LANDINGS, RAMPS
STUCCO OVER FOAM INSULATION
STRUCTURAL INSPECTIONS & DEFECTS
SUMP PUMPS GUIDE
THERMAL TRACKING & HEAT LOSS
VAPOR BARRIERS & AIR SEALING at BAND JOISTS
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VAPOR BARRIERS & HOUSEWRAP
VAPOR CONDENSATION & BUILDING SHEATHING
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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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• 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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