At Small Planet Supply we get a lot of inquiries about using ThermaCork for soundproofing applications. With noise pollution increasing, even while other forms of pollution are remaining steady or decreasing, finding ways to turn down the volume is important. A 2011 World Health Organization study ranked traffic noise second in environmental threats to the public, only surpassed by the danger of air pollution. If you’re already trying to cut down on harmful VOCs, solvents and environmentally destructive production processes in your home or project, the next logical step is to design for noise reduction.
SOUND MANAGEMENT FUNDAMENTALS
First, let’s distinguish between soundproofing and acoustics management. Sound is vibration waves in a medium. The medium we generally think of is air, but sound also travels through solid materials. This means that when sound waves hit a structure, they continue to propel through the building materials, while also reflecting off building materials. This means two different activities are occurring simultaneously in situations where we are trying to attenuate the sound. Soundproofing involves sound penetration and acoustics management involves reverberation and absorption. It takes a LOT of work to make a room completely soundproof, but you can attempt to address both soundproofing and acoustic management in your home or project.
MANAGING SOUND REVERBERATION
We’re going to talk about the acoustics first, as it is easier to diminish reverberation than to block sound all together. ThermaCork helps with reverb by absorbing a percentage of the sound energy. The absorption of sound energy is measured by the Noise Reduction Coefficient (NRC). The NRC represents the percentage of sound absorbed, with 0 being no absorption (perfect reflection), and 1 being the best case for sound absorption. ThermaCork High Density at 50mm has an average rating of .41 NRC; for comparison, drywall boards have an average NRC of .04. This means ThermaCork absorbs nearly ten times more sound than the most common wall covering!
Remember that sound moves in waves, and for us to hear that sound, all the waves need to reach our ears intact. When sound waves are disrupted, we perceive this as sounds being muffled or eliminated entirely. Cork works well because it is comprised of many cells surrounding pockets of air, and along with being a great thermal insulator, air is also a good noise insulator. Each of these cells absorb and diffuse vibrations, thereby interrupting the sound waves and diminishing further travel. Combine that effect over thousands of cells and you have very efficient acoustic dampening.
To further diminish reverberation, you can also try to vary the shape and contour of any wall panels. This works to increase the total surface area available for sound absorption. More surface area equals more total sound absorbed and not reflected. In addition, this will also aid in blending and dispersing the sound waves that are reflected, this can greatly reduce sound waves and echoes. Further covering of the cork with a fabric can add even more absorption and diffusion to go the extra step if cork alone is not enough to help with echoes.
Up to this point we have been addressing methods of mitigating sound reverberation, but what if you want to eliminate all sound transmission (soundproof)? This is where things can get a little more difficult, as it takes a lot of work to stop sound transmission completely. You can certainly work to lessen it to a degree though. To effectively block sound, you need to employ several methods.
STRATEGY 1: MASS
The first and most basic, but major factor, is mass. You want lots of mass between the sound source and the listener, as this mass will greatly slow the propagation of sound waves. The most ideal product for this would be some type of Mass Loaded Vinyl, which is a vinyl sheet produced to be as heavy as lead is per square inch! You can also use wool batting to get a leg up on traditional fiberglass’ acoustic properties, and of course, ThermaCork will add mass. Barring a highly specialized product, there are a few other ways to help alleviate the ingress of noise into your space.
STRATEGY 2: AIRTIGHTNESS
While ThermaCork is going to stop some of the sound from transmitting through walls and floors (upwards of 40 dB), it can help to employ other methods in addition. We’ve already addressed mass, which can be added during construction. Another consideration is airtightness, which if you’re reading our blog is hopefully something you’re already trying to accomplish. Remember, sound is vibrations traveling through air, so by making an enclosure airtight you can limit ability for those waves to travel. Even with all the mass and sound absorptive material you can fit in a wall, any air gap or penetration provides a “flanking” path for sound to transfer from one space to the next. You’ll want to especially pay attention to your window and door areas. If you’re not going to address airtightness, you might as well be wasting any of the effort towards soundproofing. A 1% gap in a sound/air barrier will transmit 50% of the sound energy through it! To this end, you can find all the materials you need for airtightness on our website.
STRATEGY 3: MECHANICAL SEPARATION
The last method we want to touch on is mechanical separation. We’ve gone through various methods of absorbing sound and blocking it’s path, but one of the best ways to stop sound is by separating the layers of a structure. This is done in several different ways. One method involves adding a damping agent between layers; for instance, Green Glue or a similar compound, between two layers of drywall, or even cork, works to reduce vibrations by preventing them from transferring between the surfaces. When vibrations hit a surface, they transfer the energy to it, potentially allowing the sound to amplify and propagate through the wall. By separating the layers, we not only absorb sound and prevent surface to surface transfer, but we also improve overall Noise Reduction Coefficient and Sound Transmission Coefficient. This is because layers of separated mass stop more sound wave energy than an equal mass of a single layer.
Other methods of cutting mechanical ties include using a staggered stud wall and using isolation clips. Isolation clips aid in decoupling the physical structure by “floating” your walls and ceilings away from the studs, further reducing the transfer of vibrations through a structure.
COMBINING METHODS FOR THE BEST RESULTS
By now you can see that it takes a system of materials and methods to construct a soundproof wall. While you will get the maximum amount of noise reduction by employing all the methods covered, it is still possible to mitigate sound with a selection of the various methods. Furthermore, ThermaCork panels themselves will dampen the range of the human voice extremely well, so if that is your main goal, we’ve got you covered.
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