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  1. 

    How MLV Works

    Mass loaded vinyl is available online through many sources and nearly each source has their own name for this material. MLV, acoustic barrier, and probably 25 different brands. Ultimately, if it's a 1 LB vinyl, then it's a 1 LB vinyl. Very little difference from manufacturer to manufacturer and no noticeable difference in performance, appearance, or other product specs. In this article, we're going to simply refer to this material as MLV.

    WHERE SHOULD MLV BE USED

    MLV should be used in two types of applications: 1) Simple assemblies that have limited to no other sound control products and 2) Assemblies that have resonance issues.

    SIMPLE ASSEMBLIES

    Simple assemblies include assemblies that have: limited mass (single layer drywall on each side of the wall), no other sound control products (damping compounds, resilient clips), and areas where other products can't be installed (around duct work and pipes, over doors and windows, or sewn into curtains).

    RESONANCE ISSUES

    Installing the same material over and over again, like 3 layers of 5/8" drywall back to back, will improve low frequency isolation because of the all the mass. But the resonance issues of 5/8" drywall are made worse when multiple layers of the same material are included in the same assembly. This is true for any rigid building material, whether drywall or wood, in any thickness.

    WHY MLV WORKS

    MLV is an acoustically dead material, meaning that it does not resonate like common building materials. All rigid building materials have resonance issues. A single layer of drywall will provide a similar STC rating to 1 LB MLV, but that single layer of drywall will perform inconsistently (resonance issues) at various frequencies. Meaning it might test well for an STC rating, but not perform well in the real world. Combining MLV in a simple wall or ceiling assembly will provide significant gains. A wall with a layer of drywall on each side will have an STC rating of 35. Option 1, include 1 LB MLV on one side and the STC goes up to 44. Option 2, add just a second layer of drywall on one of those sides and the STC rating only bumps to 37. What this means for you is that the MLV can double the performance of a common wall while a second layer of drywall will only slightly improve the wall. Possibly not even enough for most people to notice.

    In other simple assemblies, such as wrapping duct work, drain pipes, hanging over doors, windows, or curtains, there simply isn't another solution that works. The flexibility of MLV and ability to tape or adhere to virtually any surface gives MLV a distinct advantage over other products on the market. MLV can also be customized to included quilted fiberglass to improve decoupling, fabric to reinforce the MLV, and aluminum or foil/scrim faced options. All of these types of MLV are available on our site.

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  2. 

    Improving Performance of Rubber Underlayment

    IN CONCRETE STRUCTURES

    Concrete structures have lower IIC ratings (approximately 28 to 35 IIC) than wood structures because they are more rigid and massive. For those same reasons, concrete structures also respond best to resilient sound isolation products like rubber underlayment because the added resilience provides something sorely lacking from the basic concrete structure. When combined with the extreme mass of the concrete, the resilient rubber underlayment adds high levels of isolation for footfall impact noise transfer.

    The easiest way to increase the performance of the rubber underlayment over a concrete sub-floor is to install a thicker rubber or a double layer of rubber to create double deflection.

    IN WOOD STRUCTURES

    Basic wood structures start with higher IIC ratings (approximately 40 to 45 IIC) than concrete structures because they are lightweight and will flex. Installing rubber directly to a wood sub-floor will achieve less dramatic IIC gains than in concrete structures. This is because when someone steps on the rubber, the wood beneath will also give. As opposed to concrete structures, which have little or no give. The two best ways to resolve the flex in wood structures is through stepped blocking between the joists or layering mass over the sub-floor.

    STEPPED BLOCKING
    Fixing structural deflection can be resolved with stepped blocking. Stepped blocking is the process of increasing structural stiffness by adding framing within the joist cavity running perpendicular to the joists. This stepped blocking is the equivalent of another beam in the middle of the joist system. The rigidity created with stepped blocking takes the ‘give’ out of the wood structure allowing the rubber underlayment to deflect (compress) properly.

    LAYERING MASS
    Layer significant mass, approximately 7 pounds per square foot, directly to the sub-floor or over the top of the rubber underlayment. Any heavy material will work, i.e. plywood, OSB, MDF, drywall, lightweight concrete (best option of course), or a cementitious board like HardiBacker.

    Layering the mass directly to the sub-floor will help most with isolating low frequencies for both airborne and footfall impact noise transfer. Most severe sound issues are low in frequency. Layering the mass over the rubber underlayment will lose some performance in low frequency isolation, but gain some performance in the mid to high frequency range.

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  3. 

    Scam Underlayment Ratings

    Acoustic underlayment increases IIC and STC ratings in floors. With the many different acoustic underlayment products, there seems to be some debate on which material works best in floors, as well as the legitimacy of the ratings for these products. We can help resolve some of this confusion.

    SCAM/BOGUS UNDERLAYMENT RATINGS

    Some distributors and manufacturers will promote unusually high STC and IIC ratings for floor underlayment products. We believe these ratings perpetuate largely from a lack of understanding for what the ratings represent. Isolation products for walls will occasionally have ratings that are misleading, but rarely to a point of ridiculousness. Marketing for floor underlayment products, however, will claim ratings that are several times better than what is even physically possible in a structure. A few minutes of searching online will result in at least ten random underlayment materials with STC/IIC ratings north of 70. To add to that, most of these 70 plus STC/IIC rated products are only 1/16” thick, or at most 1/4” thick.

    To understand how misleading these claims are, we have tests for 2” of solid rubber over 6” of concrete and 4″ of concrete poured over the rubber performing at IIC 64 and STC 72. Now the STC rating was able to get above 70, but only with 10” of concrete and 2” of rubber. Reduce the thickness of the rubber to 1” and the rating drops to STC 69. Reduce the thickness again to 3/8” and the rating drops to STC 54. From this, it is obvious to anyone with a little sense that if 2” is STC 72, 1” is STC 69, 3/8” is STC 54, then there is no way 1/16” of any material is anywhere near STC 70 plus.

    CHARACTERISTICS OF A QUALITY UNDERLAYMENT

    Starting first with the characteristics of an underlayment suited for isolating impact footfall noise. Resilience is key to isolating impact footfall noise as it allows a cushion for the energy of sound (pressure of a footstep). Proper resilience can be created within a remarkably thin profile assuming that layer is truly resilient. Meaning it can properly deflect (compress) when put under stress and return to the original form when not under stress. A proper underlayment does not need to be soft like carpet pad, but must be resilient like rubber. Flexible vinyls, cork, rolls of composite material, or similar, are not significantly resilient products.

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