Photograph of sound and noise control measures for buildings.Guide to Sound Control in buildings: Sound Transmission
     

  • SOUND CONTROL in buildings - home - CONTENTS: Principles of sound transmission in buildings. How to make a building quiet: sound isolation strategies. Sound insulation designs for building walls. Sound control for building floors. How to control plumbing noises & sounds. List of soundproofing materials. Tables of sound control data for buildings
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Building Noise & Sound Control: This article series presents methods and materials used to control sound transmission in buildings: how to make a quiet home, office, or place of business using sound isolation for ceilings, floors, walls, plumbing, etc.

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Quiet Please! Best Practices Guide to Sound Control in buildings

This article series discusses noise and sound control in buildings, and includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons. The page top illustration from the above text shows an example of a design to reduce transmission between building floors.

Because of its stiffness, wood framing (photo at left) readily transmits low-frequency sounds and impact noises through wood- frame houses. This is particularly a problem in floors and walls separating two housing units, but it can also be an issue within a single-family home.

For example, a person with a home office or music room might want to isolate it acoustically from the surrounding rooms so meetings or music proceed in private and so outside noises will not intrude.

Bedrooms located under living spaces can also require special treatment to reduce impact noises from above.

Another kind of noise control is important where a house sits by a highway or under a flight path.

The goal here is to keep outdoor noises from entering the house by reducing sound transmission through windows, doors, and exterior walls and ceilings. Special acoustical windows rated for low sound transmission are often required for substantial reductions in outside noise.

Principles of Sound Transmission

Sound can travel through both air (airborne sound) and solid materials (structure-borne sound). Structure-borne sound can be directly imparted to the building structure by a vibration, such as a humming compressor, or by direct impact, such as a boot stepping on a hardwood floor.

As sound energy travels through a building, it changes from one type of transmission to the other and back, losing energy in each transition. Because of its rigidity, wood framing is a very good transmitter of low-frequency sound and hollow wall cavities and thin doors do little to reduce sound transmission.

How Sound Levels are Measured in buildings - What is a Decibel

Table of typical sound levels in decibels dB (C) J Wiley & Sons Best Practices Steven BlissSound levels are measured in decibels (dB), which are on a logarithmic scale. A sound increase of just 10 dB indicates an increase of ten times the intensity, although our subjective experience is that the sound is twice as loud.

Decibel levels for common sounds are shown in Table 5-14 at left.

Continuous exposure to sounds above about 85 dB can cause hearing loss in most people.

Sound Absorption vs. Sound Isolation in buildings

Sounds in an acoustically “live” room with all hard surfaces will seem loud and harsh due to the sound reverberating off the hard surfaces.

Adding sound-absorptive materials, such as carpeting and soft furniture, will make sound softer and more pleasant within the room, but will do little to reduce the transmission of sound to adjacent rooms.

To reduce transmission requires sound isolation strategies, typically using high- mass materials, double-framed walls, or resilient connections between the drywall and framing.

Sound Isolation Strategies for Indoor Noise Reduction

To keep airborne sound from passing through walls and floors, there are four main strategies:

A cavity with fiberglass is far more effective at blocking sound if the two wall surfaces (or ceiling and floor surfaces) are mechanically decoupled as in a double-stud or staggered-stud wall. Resilient channel works essentially the same way by breaking the vibration path from the stud or ceiling joist to the drywall.

The hardest sounds to block are low frequency, such as the thumping of a stereo bass. Using decoupled construction, such as double walls or resilient channels, is effective.

Where that is impractical, adding mass can also be effective. Very massive, non rigid materials such as lead or sand are ideal, but doubling or tripling the drywall is also helpful.

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

 

Continue reading at ACOUSTICAL SEALANT CHOICES

Other noise and sound diagnosis and control articles are found at NOISE / SOUND DIAGNOSIS & CURE where we describe how to locate the source of, identify and correct various building sounds and noises indoors or on occasion, noises from outside that penetrate indoors at annoying levels.

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