Our Opinion Of Various Sound Isolation Products

Numerous tests have been done to show that the performance from the type of insulation you use in your wall varies very little from one insulation to another. The use of insulation is very important, no argument there, but the type of insulation used really does not matter as long as it is light, fluffy, and sized to fit the cavity (ie, R-13 in 2x4, R-19 in 2x6, R-19 or R-38 in a standard ceiling joist cavity). Compacting insulation, for instance R-19 in a 2x4 wall, can actually hurt performance as the insulation density will increase which will result in conduction between the insulation and adjacent framing/drywall. Specialty insulation does have its place in construction for various reasons, increased energy efficiency, fire rating, easier installation, no chemicals or less chemicals, and to avoid the dreaded itch from fiberglass.

Our Advice: Save the cash on the fancy insulation and put it towards products that will provide a much larger boost in performance.

This product known as 'sound board' is distributed at home improvement stores, drywall distributors, and other stores online. Performance from sound board and sound board type products have no real place in wall and ceiling construction. Any panels hung on your walls and ceilings should have as much mass as possible. Sound board has very little mass so including a layer of sound board will not increase performance any more than a single layer of drywall. Some increase in performance is had by the very light decoupling it can provide between drywall and framing, but those gains are quickly lost due to the product's severe lack of mass.

With that said, including sound board in your floors will have a decent increase in performance. It will not be as significant as QuietGround Rubber Underlayment or Green Glue Compound in your floors, but it will perform noticeably better than just another layer of plywood.

Our Advice: Sound board, and similar sound board type products, are okay for floors, but a waste of time and money in your walls and ceilings. If you want layers then stick with something that is cheap with higher mass like drywall.

Cork underlayment is often passed off as a product that can isolate sound. At best it can help to reduce footfall noise, but only if you install a very thick cork underlayment (ie, 1/2" or thicker). Installing a 1/2" of cork is just barely equal to less than a 1/4" of rubber underlayment. Cork has little ability to isolate airborne noise given its lack of mass. Similarly to sound board it offers a little bit of a separation between flooring and the sub-floor so there is some performance gain in floor installations. We used to offer a line of cork underlayment with little satisfaction from customers. We quickly discontinued the line and kept with our QuietGround Rubber Underlayment which has always received high praise. Cork underlayment is advertised as anti-microbial, but more and more cork is shipped from overseas where true cork trees do not originate. The quality of this overseas manufactured cork is low and unpredictable. Because of this, cork underlayment has been banned from many large multi-housing projects and in some cases banned by various building departments in the United States.

Our Advice: Cork is really cheap so it is appealing. If you are trying to isolate footfall noise then you can buy really thick cork and get okay results. However, a 2 MM QuietGround 125 Rubber Underlayment will perform as well as a 6 MM cork and cost quite a bit less. To us the rubber is a smarter choice because it will not build up your floor height nearly as much and the cost will be less. If your goal is to block airborne noise then steer clear of cork altogether.

Any rating you find online for an underlayment of any kind (unless extremely thick, ie, 1"+) that provides an STC and/or IIC rating well into the 60's or above without acknowledging any other included products is purposely misleading. All sound isolation products are limited by basic physics. There is no underlayment that exists that can rate 10 points higher in a floor than another quality product without including a treated ceiling below or a really thick floor construction including thick concrete, 1 1/2" GypCrete, and layered plywood. Our QuietGround Rubber Underlayment, depending on thickness, can achieve ratings in the mid to high 50's STC and mid to very low 60's IIC (only with concrete sub-floor). Ratings well into the 60+ range require additional products or a more complicated construction style which often is not possible for the average customer.

Our Advice: This only requires a little thought into what can make one product so much better than another. If your faced with an oddly well performing product then sit back and analyze what could possibly make the product perform so much better than other products. We have seen ratings online for 1/16" thick mass loaded vinyl based underlayment with a 70+ STC rating. How could a 1/16" vinyl underlayment block more sound than regular 1/4" vinyl? The only way it could is if the 1/16" vinyl underlayment was able to defy the laws of physics.

Resilient channel really is not that bad of a product to use in walls. Realistically you can bring up the rating of a wall by a good 12 STC points. Note that there will not be much improvement at all in isolating low frequencies. The STC increase might just be enough for you if you need to block some low level sound transfer such as people talking in the next room, phones ringing, or light TV noise. Resilient channel is difficult to install and nearly impossible for a DIY homeowner to install correctly without prior knowledge of drywall and the common pitfalls of resilient channel. Because of this we would definitely recommend the use of our RC Assurance resilient channel clips. You'll need quite a few of them even for a small wall, but they are very cheap and they will guarantee a properly installed resilient channel.

Now resilient channel can do well in walls, but it will not do much in ceilings. Ceilings are a whole other beast in the world of sound isolation and the flimsy resilient channel decoupling the drywall by just a 1/4" adds an insignificant amount of resiliency to a 12" thick wood framed floor. Airborne isolation will improve with ceiling installation, but not by much. Footfall impact noise isolation will not be affected enough to satisfy the majority of customers.

It's always good to point out that importance of avoiding installing resilient channel or any decoupled system over existing drywall. This causes all sorts of issues with resonance (triple leaf effect) and the end result is a void gain from using resilient channel. Resilient channel can increase performance in a wall by 12 STC points, but if installed over drywall to cause a triple leaf then the performance will be brought down roughly 10 points. Overall gain will only be 2 points. Resilient channel in a ceiling will only bring up the performance by about 5 points so if you install the resilient channel to cause a triple leaf then you might be worse off from when you started.

Our Advice You can do pretty well using resilient channel in walls as long as you install it properly. Use the RC Assurance to guarantee success or really take your time installing to make sure you do not short out your installation. Installing resilient channel in your ceiling will not provide great results and no real improvement for footfall impact noise. Resilient channel is a decent solution for sound isolation in walls, but there are better products out there that do not really cost more as well as products that have easier, more fail-proof, installations.

Some project specs call for resilient channel with a thin foam installed on the channel and/or between the channel and framing. Some manufacturers have put together a resilient channel with foam or rubber pre-attached along with a foam or rubber base to install between the channel and the framing. This seems like a great idea, but in the end all you will end up with is the performance of basic resilient channel. No true sound test would show otherwise.

Our Advice: Do not bother with these types of products. Go ahead and use resilient channel, but do not think that using foam on the channel will actually give you a jump in performance beyond an inaudible 1 STC point gain. The reason why these types of products exist on the market is because it is nearly impossible to make a profit off selling resilient channel unless you are a local distributor. To compete online, companies had to come up with a way to alter the resilient channel to make it more appealing than basic resilient channel.

As long as you can provide the labor, a staggered stud or double stud wall is an affordable way to decouple your walls. Retrofit installations of staggered stud walls and double stud walls will still require you to remove the drywall from the existing wall to avoid causing resonance issues. Performance of a staggered stud wall is near that (about 2-4 STC points better) of double layer drywall and Green Glue Compound on a standard wall. Combining the two will create a high performing wall with isolation over a wide range of frequencies. Double stud walls will perform noticeably better than staggered stud walls as long as the gap between the two framed walls is at least 2". Two 2x4 walls and a 2" gap between will create a wall that is over 9" thick. Overall performance will be in the high 50's to real low 60's in STC for a double stud wall with a 2" gap. The GenieClip on a standard wall will add 1 1/2" to a wall's thickness and provide performance at 64 STC with roughly the same performance in low frequencies.

Our Advice: Staggered or double stud framing can be a very cheap way to isolate sound efficiently. Resilient sound clips will outperform both staggered and double stud framing while taking up less floor space than both options. If you can afford to lose the space then a double stud wall with a 3" gap between each wall might just be the best solution for you. Staggered and double stud walls do not address sound transfer in ceilings so you will likely end up having to treat the ceiling with clips to match or exceed the performance of the specialty framed walls.

It is a very bad idea to install recessed lighting in a sound rated ceiling and not treat the back of each recessed light. The loss of mass is the biggest issue and needs to be restored properly to avoid sound leaks through the light housing. There are a couple solutions on the market that look basically like an fibrous insulation hat that sits on top of the light housing. These products might help a little, but ultimately not much more than overlaying the light with insulation. What is lacking from these products is mass. These products try to use absorption to isolate sound which does not address the actual problem caused by the recessed light which is the lost mass.

Our QuietBox solution restores the mass in line with double layer 5/8" drywall with Green Glue Compound between each layer. And just as important, the entire box is decoupled from the joists using resilient clips with the box being sealed to the back of the ceiling drywall.

Our Advice: You do not have to buy a QuietBox to isolate your recessed light, you can make your own if you want. Any other solution though will not properly address the lost mass from the recessed lighting. If you design your own box then be sure to follow the requirements of restoring ceiling mass, decouple your solution from the joists, and make sure to seal the box to the drywall to avoid sound leaks.

When you purchase brand name mass loaded vinyl (MLV) you are buying into a brand rather than buying a product that actually performs better than much cheaper private label mass loaded vinyl. The brand name MLV that costs anywhere from $2 to $4 per square foot for 1 LB material has very few differences from private label MLV. Brand name MLV is manufactured using 100% or near 100% flexible PVC. This creates a product that is slightly more flexible and a little stronger as well. These attributes might sound like drastic improvements over private label MLV, but in the end once you install the MLV in your walls, ceilings, or floors, the results will be the same. The increased flexibility might help with performance by 1 or 2 STC points (non-audible improvement) when installed limp (ie, draped around pipes, hung as curtains, or on fences), but when it comes to rigid installation which accounts for almost all MLV installations, the fancy brand name MLV provides no actual increase in performance.

Our Advice: When it comes down to it, the biggest difference with brand name MLV is the price. Overall, the material is the same as private label MLV. Brand name MLV is often manufactured by the same companies that manufacture the private label MLV - hence the private label tag. The truth about MLV is that it is limited in performance whether you buy brand name or private label. With each passing day it is less and less popular compared to new, cheaper, and more efficient solutions like Green Glue Compound and resilient sound clips. You can pay 2-3 times as much to get a slightly non-audible improvement in performance or you can put that money towards a resilient sound clip system which would be considerably less in price and several times higher in actual performance.

We have helped several customers design and build recording booths for their home. A few of these customers had previously invested in the pre-fab isolation booths that you can find online for thousands of dollars. After purchasing a pre-fab unit they came to us to try and design/build their own booth due to dissatisfaction with the sound isolation capabilities of the pre-fab unit. We are not surprised by their dissatisfaction based on the materials used in these isolation booths. Acoustic foam, insulation board, and mass loaded vinyl are typically the main materials used. These products can help isolate the highest of frequencies and absorb some of the reflections to improve acoustics, but for actual sound isolation these designs really are not adequate.

Our Advice: If you need a temporary booth or a semi-mobile booth then it seems like the pre-fab route would be a good bet even with the limited performance. If you really want to isolate sound then you need to build a booth following the basic principles of sound isolation. Frame a booth with decoupled walls either using staggered stud walls, double stud walls, or resilient sound clipped walls and then incorporate, at minimum, mass through multiple layers of drywall on the outside of the booth and the inside of the booth along with insulation between the stud cavities. The inclusion of damping from Green Glue Compound is popular as well, especially in floors where decoupling is much more difficult.

The concept of pre-damped engineered drywall is not really much different than Green Glue Compound between two layers of drywall. Pre-damped drywall will perform better than resilient channel and better than mass loaded vinyl, but there are some problems with this approach that should be pointed out. Here's a short list:

• Damping adhesive used in pre-damped drywall is not nearly as efficient as Green Glue Compound resulting in lower performance regardless if installation is successful.
• Only one layer of material is hung which increases risk of a faulty installation. Installation installations include requirements to use an expensive acoustical sealant on the perimeter of each sheet before hanging along with thin lead strips behind each joint.
• Pre-damped drywall is very heavy and the most commonly purchased style includes a cement board backing that can really only be cut with a circular saw rather than a razor knife like you can with any standard drywall.
• Labor is saved by not having to apply the Green Glue Compound, but savings from this are quickly lost because of the weight of the material being hung and the difficult in cutting the material.

Our Advice: Green Glue Compound with double layer drywall is roughly 35% less than pre-damped engineered drywall solutions - this includes all materials and labor. The Green Glue Compound solution costs less, performs better, easier to install, and no risk of installing incorrectly unless you forget to apply the glue. Given this, why would anyone use pre-damped engineered drywall to isolate sound? Our experience is that many will try the pre-damped drywall, but few will continue to use the pre-damped drywall out of frustration for the many pitfalls of the pre-damped drywall solution.