Our Homes are oftentimes the centerpiece of privacy, solitude, and rejuvenation. We count on our home for rest and stillness apart from the noisy and busy world we visit each day. Strangely though, precious little attentions is paid to ensuring that our spaces are shielding us from the many sounds that make their way through our walls - the neighbors lawnmower, a barking dog, a nearby highway, or passing emergency vehicles all infiltrate our walls and disturb that interior stillness.
There are a number of low-cost means for reducing outside noise and working these into the design process of your new home is the best time to do it. Below we’ll explore a few of these methods. First, let‘s take a quick look at what ‘noise’ is and how it gets into our home.
The Problem of Noise:
Our homes are our sanctuary, but typically very little in done to really deal with outside sound.
Standard home construction in the Unites States involves an exterior wall assembly of the following:
2” x 4” wood stud framing,
R-13 Fiberglass batt insulation,
One layer of 1/2”-5/8” OSB or plywood sheathing,
Siding on the outside, and
Drywall on the inside.
This assembly reduces sound by about 40 decibels. That’s enough to shield you from a whispered conversation. But the world outside is hardly a whisper. For perspective here are some common sounds and their decible levels:
Whispered speech: 30 dB
Normal speech: 60 dB
Household vacuum cleaner: 70 dB
Phone ringer: 80 dB
Gas Lawn Mower: 90-106 dB
Car horn: 110 dB
Leaf Blower: 95-115 dB
Ambulance siren: 120-130 dB
Hearing damage begins at about 70 dB. 70!
A decible, by the way, is the unit used to measure the intensity of a sound (read: volume). It is abbreviated as ‘dB’.
The reality is that our homes are doing precious little to block all that noise pollution. Fortunately, there is a lot we can do to improve this in the building process and significantly reduce noise infiltration into our homes.
Understanding Sound & Materials:
Sound is energy transmitted as a wave through a ‘medium’. That energy wave vibrates matter (the ‘medium’) at a particular frequency. Higher density mediums, like water, transmit those vibrations better that lower density mediums, like air. This high density/low density rule comes with a caveat though - very high density mediums do not vibrate well and therefore do not transmit sound very well.
Here’s another thing about vibration - it requires consistency or ‘coupling’ through the transmission medium in order to keep the vibration moving along. Break that connection between materials and the energy fueling that vibration takes a hit.
Sound Infiltration & Mitigation:
So, interrupting the transmission of sound, as it vibrates along through different materials, is our project. Lucky for us, there are a number of materials and methods available to help us.
These materials and methods are largely organized into one of two categories:
Dampening, and
De-coupling
Dampening is the use of materials that don’t vibrate well. This includes things like concrete, layers of drywall, packed soil, etc.
De-coupling is the use of materials and methods that separate materials from one another so that the vibration is interrupted as it moves along. Used in concert, dampening and de-coupling can make a huge impact on sound reduction.
Sound infiltration is when sound makes it way through a barrier, like a wall. Similar to heat, cold, or air pollution (think smoky skies in August), unwanted noise also leaks into our homes.
Options for Reducing Noise
Now that we understand what’s happening, here are some building solutions to Dampen sound and De-couple materials in your new home.
Drywall
Gypsum Wallboard or ‘drywall’ is a dense material and can help reduce sound. Thicker, 5/8” sheets, double layered provide a dense layer to dampen sounds. Look for Type X drywall designed for fire suppression as this provides the best density.
Mineral Wool Insulation
Made from a mixture of rock, blast furnace slag, and other raw materials, then spun into fibers that resemble the texture of wool. The superior density of mineral wool makes it much more effective that standard fiberglass insulation for dampening sound.
Upgrade to 2x6 Walls
Thicker walls allow for more space for additional sound-dampening insulation. Just 2 inches thicker than a 2x4 wall yet capable of reducing sound up to 30% better.
Double Stud or Staggered Stud Walls
Constructing two stud walls in parallel, but not touching, creates a dead space in the cavity between the walls. Insulate both walls, and add a layer of 5/8” Type X drywall, and sound energy will li
terally hit the wall when trying to cross that gap.
Similarly, building a wall with staggered studs helps to de-couple materials, reducing the transmission medium and deadening sound energy as vibrations transfer across materials.
Resilient Channel or ‘Hat’ Channel
Add resilient channel between framed walls and drywall. This hat-shaped metal channel de-couples sheetrock from wall studs by adding a steel barrier that inhibits sound vibration across the two materials.
Carpet or Cork Flooring
Solid-surface floors can reflect a lot of sound within a space. While having little to do with sound infiltration, the choice of flooring can go a long way toward softening the sound inside the space. Carpet with foam padding underneath or cork flooring are both great options for absorbing sound.
Average Sound Reduction (in dB) by Material
Material Type | Reduction (in Decibels) |
Cork Flooring (10mm thickness) | -40 dB |
Laminate Flooring | 0 dB |
Hardwood/Engineered Flooring | 0 dB |
Wood Framed Wall/Ceiling | -25 dB |
Mineral Wool Insulation | -25 dB |
Drywall - 5/8”, Type X (two layers) | -10 dB |
One-Legged Resilient Channel | -10 dB |