It’s pretty likely that your house is made of wood. Wood is a common and cost-effective building material that allows homes to be built more quickly than homes made of concrete or steel. Over 90 percent of American homes are built with wood, according to the Western Wood Products Association, making it the most common building material used for houses. But how effective is this material at keeping unwanted noise out of your room?
Wood is not as soundproof a material as concrete or steel but can be a viable material for soundproofing when combined with other construction materials and soundproofing techniques.
You may be concerned about reducing interior sound from noisy children or roommates, or exterior noise from street noise and traffic. While wood is one of the most inexpensive building materials, it may not be the best choice of material if you’re looking to have soundproof rooms. There are many factors that go into whether or not a certain material is soundproof, and there are ways to make wood material more soundproof by changing it or combining it with other materials.
How Soundproof Is Wood
While wood has the ability to reflect sound, it’s not the best material for soundproofing. Using thicker wood, such as a heavy wooden door, may be able to block sound well enough to soundproof a room. The best types of wood materials for soundproofing are cork, acoustic plywood, medium-density fiberboard, and oriented strand board, according to Soundproof Central.
Measuring Materials
In order to measure how soundproof the material is, soundproofing experts use a measurement called Sound Transmission Class (or STC). This measurement is used in many building specifications and regulations and is a building standard issued by the American Society of Testing and Measurement (ASTM). STC measures the amount of decibel reduction a material can provide to noise. A higher rating shows better soundproofing ability than a lower number. Materials with an STC rating higher than 60 are great for soundproofing. [Source]
| STC | Sound-Blocking Effect |
|---|---|
| 20-25 | Quiet speech is audible |
| 25-30 | Ordinary speech is audible and intelligible |
| 30-35 | Loud speech is audible and intelligible |
| 35-40 | Loud speech is heard but is rarely intelligible |
| 40-50 | Loud speech can be heard, faintly |
| 50-60 | Loud sounds can barely be heard |
How Does Wood Measure Up
When compared to other common soundproofing materials, hollow and solid wood is on the lower end of the scale but improves with more dense and thicker wood material.[Source]
| STC | Material |
|---|---|
| 0 | No insulation barrier |
| 20-25 | Hollow wood door |
| 30-35 | Solid wood door |
| 35-40 | Standard wall |
| 36 | Fiberglass insulation |
| 41 | Closed-cell spray foam insulation |
| 45 | Thick wood door |
| 45 | Denim blue jean insulation |
| 50 | Rock wool batt insulation |
| 50 | Open-cell spray foam insulation |
| 50 | Cork underlayment |
How Does Sound Proofing Work
Materials have the ability to either reflect or absorb sound. Sound waves have the ability to bounce off of surfaces that are smooth, such as wood planks or flat plywood sheets. Materials that absorb sound are able to control noise in the room by reducing echoes, but they don’t prevent the noise from leaving the room. If you want to stop noise for entering or exiting the room, you’ll want to use a material that is able to block sound altogether, such as dense, heavy, solid materials. [Source]
Sounds have different frequencies that require different materials to absorb them. Low-frequency sound waves have low, “rumbly” tone that has longer wavelengths than medium to high frequencies. Low-frequency noises are more difficult to soundproof because they can pass through materials more easily than higher frequency noises. It is best to use a material that will absorb the sound waves or increase the thickness of the walls to soundproof low-frequency sound.
The best material for soundproofing is one with an uneven surface that is able to break up the sound, paired with an extra layer of something full of air, such as thermal insulation, and something heavy and strong, like a concrete wall. Wood is typically light, making it an unideal material to block sound. It’s also usually too smooth and dense to absorb sound. As a generally porous material, wood is better at reflecting sound waves than absorbing them.
Acoustic Properties of Wood
Acoustic properties tell us how different materials respond when coming in contact with sound waves. Because wood is a porous material, it is better at reflecting sound waves than absorbing them. It conducts sound waves better in the longitudinal direction of the grain rather than perpendicular to it.[Source]
Wood that is quite dense can reflect sound and can be made into surfaces to channel sound reflections. This technique can be used in concert halls and some types of musical instruments.
Wood is often used for musical instruments because it is lightweight and much easier to cut and shape than metals. It is also ideal for instruments because the combination of reflection and curved surface makes a great sound. Wood that is dense is ideal for musical instruments because of its ability to reflect sound.
The Noise Reduction Coefficient (NRC) measures the acoustic properties of different materials by comparing the amount of sound reflected to the amount absorbed. These measurements are on a scale of 0 to 1, with 0 being no sound reflected or absorbed and 1 being all sound reflected or absorbed. If the wood material has a smooth surface, the NRC value is typically about 0.05 to 0.15, according to Better Sound Proofing.
Thicker wood increases sound absorption and therefore increases NRC value. Adding acoustic wooden panels, when placed correctly, can improve the absorption value up to 0.90. These acoustic panels should always be placed with the help of a qualified sound engineer.[Source]
How To Make Wooden Rooms More Soundproof
On a structural level, sound insulation in wooden buildings can be increased by constructing with multiple layers. This is achieved by placing a porous absorption material, such as thermal insulation, behind the paneling along with an air gap. This forms a “board resonator,” which dampens sounds when it vibrates. This best works for low sounds. For higher sounds, you can create a “perforated resonator” by perforating the wooden surfaces with small holes. It is difficult to control sound insulation in wooden buildings with multiple stories, but it may be achieved by increasing the mass of the floor.
Wood can be made to absorb sound more easily by perforating the material with holes or grooves. You can also use other materials made from wood to dampen sounds, such as sawdust and cork boards.
During construction, another sound barrier can be added by putting sound clips or channels between wall studs and drywall. Stud placement can make a big difference in how soundproof a room is, as the sound is easily transmitted through wall studs.
Instead of building a single row of studs as in most walls, use a double row along each side or a staggered row alternating on one side. After completion of the room, acoustical caulk is a good option to prevent sound from escaping through cracks in the wall.
A number of items can be added to a room after construction to help with soundproofing.
| Acoustic panels | Can be placed on walls to diffuse sound that is reflected off the other surfaces in the room |
|---|---|
| Quilts, tapestries, heavy blankets or curtains | A cheap option to absorb sound |
| Soundproofing panels or wallpaper | A more expensive option |
| Bookcases | May also help with soundproofing by adding a sound barrier to the wall |
| Door sweep | Will help to stop noise from escaping underneath the door |
| Acoustic wedge panels | Will help to further dampen sound |
Additionally, shaky items should be firmly mounted to reduce shaking and rattling from impact noise.
While wood is not the best material for soundproofing a room, it can be a viable material when combined with other construction materials and with items inside the room. If you’re set on using wood as your building material but want your area to be soundproof, be prepared to spend some extra time adding soundproofing items and techniques.
