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.

• 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. Boise Idaho Drywall Contractor Services

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.

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.

Resilient Channel With Foam or Rubber Attached

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.

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.

Our Advice: Save the cash on the fancy insulation and put it towards products that will provide a much larger boost in performance. Or if you are working on a home theater, get a nicer sub.

The basic design of the clip is familiar with the black neoprene bumper and one screw installation. The performance increase, which is mainly found in the low frequency ranges, is largely attributed to the quality of the neoprene rubber attached to the clip. The Durometer (hardness) of the rubber is 20 points lower than the other resilient clips that incorporate rubber on their clip. That is a very noticeable difference and just part of the equation that helps the GenieClip perform at maximum efficiency. Here is an excerpt from the manufacturer’s site discussing the quality of rubber on the GenieClip:

Importance of Rubber Properties in Performance of the Resilient Clip Technology

Rubber is a superior vibration isolator. In almost every significant application, rubber is chosen to isolate vibrations because of its compression ratio, dynamic and static properties. The dynamic properties of the rubber element of a vibration isolator are affected by its compression ratio, and thus the dynamic characteristics of a vibration isolator depend on the static load.

Stiffness

The stiffness measures the “spring rate” of the rubber. Higher spring rate means a stiffer material and lower overall performance.

Static Stiffness

Under a static or constant load, the stiffness is measured.

Dynamic Stiffness

Tested under a variable load due to the effect of vibration. It is a forced frequency test for resonance at specific frequencies. Natural rubber has the lowest dynamic stiffness of common material.

Result

KINETICS: 21.6 N/MM
PAC: 21.2 N/MM
PLITEQ: 11.3 N/MM

Dynamic / Static Stiffness Ratio

The ratio is a measure of the resiliency of the material. For example, for completely resilient material, the ratio is
1. In order to achieve isolation at lower frequencies, it is important that this ratio be as low as possible. Therefore, ratio closer to 1 means better vibration isolation performance. Most acoustical engineers will specify isolators that have a maximum dynamic to static ratio of 1.4.

Result

KINETICS: 1.29
PAC: 1.34
PLITEQ: 1.19

Force / Deflection Curve

If the isolator is more resilient, typically the acoustical performance will be better. A measure of force versus deflection gives a direct link to resilience at a static loading.

Result

KINTETICS: 19.79 N/MM
PAC: 23.88 N/MM
PLITEQ: 8.95 N/MM

Durometer of Rubber

Durometer is a term for hardness as indicated by the Shore A durometer number. The normal range for isolation materials is 40 to 60+ / -5 as limited by dynamic stiffness. Steel springs for example have a ratio of 1. Dynamic stiffness increases with hardness and in broad terms, the filler ratio of the materials to the rubber content as well as the carbon black reinforcement, plasticizers etc.

Results

KINETICS: 56
PAC: 57
PLITEQ: 37

Conclusion

Based on these results, the rubber stiffness of the Pliteq GenieClip is about 2 times better than the other two materials. Since the dynamic stiffness and dynamic to static ratio control the performance of the clip, especially at low frequencies, it is clear that the performance of the GenieClip will be superior to the other two products.

The above report can be found by opening up this .PDF file: Importance Of Rubber Properties

What The Above Report Means For Your Project

The increase in performance from the GenieClip is most noticeable in the lower frequencies. The GenieClip provides a 2-3 point increase in the lowest of frequencies compared to the most popular resilient clips. The STC rating of the GenieClip is as high as 64 with an OITC rating as high as 49. The GenieClip’s ability to isolate both high and low frequencies make this clip a great option for any project. The quick one screw installation and low profile design will help you get the job done quick without sacrificing too much headroom.

A triple leaf wall is a wall with 2 air cavities, and not just one. Similarly, a quadruple leaf wall would be a wall with 3 air cavities. A leaf in a wall is a solid layer – like drywall – and (if you prefer) a triple leaf wall has 3 leaves, etc. Like this:

Here we see single leaf (no air cavity), double leaf (like most walls), triple leaf and quadruple leaf constructions. It is important to remember that if you use 2 layers of drywall directly against each other, it still only counts as one leaf because there is no air cavity between the layers. In the sketch below we show again single through quadruple leaf walls, but this time they all have the same number of drywall layers.

Why A Triple Leaf Wall Is A Bad Thing?

It is not illogical to presume that the quadruple leaf wall above would have the best sound isolation. After all, the sound has to go through a:

Solid mass – air space – solid mass – air space – solid mass – air space – solid mass

That quadruple leaf wall is decoupled 3 times over! While in a double leaf wall, it has to make it through only one air space, and in a single leaf wall there is no air space at all.

Well, while this makes sense, it is very false, especially at low frequencies. To understand why this is, we have to take a look at how decoupling works. Decoupling isn’t effective at all frequencies. If you take two layers of drywall, and separate them with an air space, it doesn’t improve things at all frequencies. The air in the cavity acts like a spring, and creates a resonance. Only well above this resonance do things improve (but then they improve very nicely indeed). This graph should make the point:

Effect Of Decoupling A Solid Mass

What you see is the sound-stopping power of the wall, in decibels, at different frequencies. This is called “transmission loss”. While this data is hypothetical, this is what occurs in real walls – the decoupling has a large positive effect at high frequencies, but a negative effect around the resonance.

Resonance Must Be Low In Frequency

To attain good low frequency performance, this resonance must be as low in frequency as possible – otherwise the weak point of your wall will fall at an unfavorable location, and low frequency noise will have little trouble passing through the wall.

The goal of any decoupled wall should be to drive resonance down in frequency. To do this you have to:

• Add mass to one or both sides of the wall
  
• Increase the depth of the air cavity
  
• Add insulation (if you don’t have insulation)

Triple leaves are bad because for a given amount of mass and space they always have a higher resonance point than a double leaf wall.

One of the criteria that were given above for getting a low resonance point – and good low frequency performance – was a deep air space, with a lot of mass on either side.

The double leaf wall might have an air cavity depth of 8”, but for the same overall net wall depth, the triple leaf wall’s cavity will be just half that, and the quadruple leaf’s cavities will be only 1/3 of the depth of the double leaf wall.

To make matters worse, each leaf in the double leaf wall is very heavy, but each leaf in the quadruple leaf wall is far lighter – half the mass. This will cause resonance to go up in frequency even more, and low frequency performance will be badly degraded.

Multiple resonances / possibly more severe resonances. To further complicate things, a triple or quadruple leaf wall may exhibit more than one low frequency resonance – and if one is bad, then two or more are surely even worse.

Finally, the resonance behavior of multiple leaf walls isn’t simple or entirely predictable, and may be more severe than with a double leaf wall.

Comparing Single, Double, and Triple Leaf Walls

Next, let’s take a look at just how bad triple leaf walls can perform relative to their double leaf counterparts.

These are tests TLF-95-107a (double leaf) and TLF-95-153a (triple leaf), taken from IR-811, a document published by the National Research Council of Canada. This data is copyright NRC Canada and shared with permission.

The difference here is stunning to say the least. It’s even more remarkable when you consider that the same type of construction, and same type and amount of materials were used in each case.

Double leaf – resilient sound clips and hat channel on joists, one big air space	Triple leaf – resilient sound clips and hat channel between drywall layers, small air space

The STC values shown above are from a series of tests run by Owens Corning in 1972 at Geiger and Hamme laboratories. While STC doesn’t tell the entire story, the point is clearly made.

Summary

Triple leaf (or quadruple or higher # of leaf) constructions should be avoided like the plague. You will always get a lower level of sound isolation, and this loss may be most severe where you need performance the most – low frequencies.

First Step: Build the Platform

Regardless of the sound isolation products you use, you will need to build a platform that is independent of the existing framing.  These platforms are typically built using 2″ x 4″  framing with 16″ on center spacing or 24″ on center spacing.  The less connection points that one material has with another the better the performance in sound isolation.  So 24″ on center is recommended, but when the platform is under 70 square feet then spacing really won’t make much of a difference at all.  The basic construction of the platform is shown in the gallery below.  Build a box frame using 2″ x 4″ studs and then connect studs 16″ oc or 24″ oc within the box.  Top this frame off with a minimum of one layer of 1/2″ or thicker sub-floor material.

Second Step: Add Something Beneath the Platform

Here’s where you have a few options:

Joist Isolators

Joist Isolator are U-shaped rubber pieces that friction fit on the bottom side of 2″ x wood products usually either 2″ x 4″ or 2″ x 6″ joists.  Using this product is cheap, simple, and depending on how much sound you need to isolate it may be effective enough to be the only sound isolation product you use if you want to keep the budget down for your floor.  A quick way to estimate the number of joist isolators needed is to take your total square footage and multiply by .65.  The smaller the area, the less likely that number will work so sometimes it is just better to draw the platform out and count how many you will need.  For small platforms you can space the joists 24″ on center, but for larger areas you will want to space the joists 16″ on center to help stabilize this floating floor design.  From there you will need one isolator on each end of the joist and then every 2′ in between.   As you can probably see if you have a platform that is only 6′ x 6′ then you will only need as few as 24 joist isolators to complete the job.  Joist isolators should be installed on hard surfaces so using this product over existing carpet will be pretty ineffective unless you were to first lay down a layer of sub-floor before setting up the joist isolator and platform system.

Rubber Underlayment

Recycled rubber underlayment is another option and typically the most common option because rubber underlayment can be applied in layers making it thicker than a regular joist isolator and because it is a more resilient product than joist isolators are.  The durometer (hardness level) of recycled rubber underlayment is almost half of what a standard joist isolator is.  Installation for this option is simple and is also pictured below.  Measure your total square footage to make sure you have enough QuietGround, cut the underlayment to size so it fits beneath the platform you create, and then lay it down on the floor before you place the platform.  The underlayment must cover the entire bottom side of the platform so that no part of the platform comes in direct contact with the floor.  Multiple layers of underlayment will improve performance and since the area you are covering is so small and underlayment typically only comes in 4′ x 25′ or 4′ x 30′ rolls we suggest using what you got.  : )

Other Options

You can add other products below this platform as well.  There are thick gym mat products, mass loaded vinyl (MLV), thick cork (6mm+),  and other ‘sound board’ type products that you can use.  We recommend the two options above over anything else because of the resiliency of rubber cannot be beat.  Dealing with deep vibrations you will need something resilient beneath the platform so the use of rubber is always recommended.  A thick gym mat can provide some decent results, but the mat will need to be over an inch thick which makes for a sometimes too cushy of an underlayment.

Third Step: Add Something On Top Of the Platform

To minimize costs you can avoid this third step.  This of course assuming you have chosen to use either joist isolators or rubber underlayment as discussed in the second step.  Like the bottom side, there are several options for the top side of this platform.  Here are a few that we recommend:

Rubber Underlayment

Rubber underlayment is superior at dealing with structure-borne noise so it is a great option for the underlayment that you install on top of the platform.  Like the bottom side, cut the underlayment to fit covering the entire top of the platform.  Multiple layers in this situation is always better than one layer so make sure to get enough!  Something thick like a 1/4″ rubber underlayment is always preferred to a 2mm or 3mm underlayment.  The rubber underlayment does not need to be attached to the top of the platform in any way.  To finish off the design you can lay a section of carpet over the platform and attach to the sides of the platform or just leave the underlayment as it is uncovered.

Mass Loaded Vinyl

A quality barrier will perform very well in this situation and since you are covering such a small area we recommend thickening up that barrier going with a 2 LB MLV over the more common 1 LB MLV.  The 2 LB MLV is as thick as one layer of QuietGround 250 rubber underlayment, but you do have the added weight with the 2 LB MLV which will help isolate more airborne noise than the QuietGround can.  The cost for the 2 LB MLV is a little more than QuietGround and if you layer the QuietGround then the 2 LB MLV will not perform better than the QuietGround.  But as a single layer underlayment, the 2 LB MLV is quite a performer!

Green Glue

The most popular sound isolation product online is without a doubt Green Glue.  To use Green Glue in this situation you will need a second layer of sub-floor screwed to the existing layer on top of the platform with Green Glue applied at a rate of either 2 tubes per 4′ x 8′ sheet or 3 tubes per 4′ x 8′ sheet.  This system will add a decent amount of mass from the extra layer of sub-floor and also the most damping that any product can provide between the two layers of sub-floor.  Performance for this option should be very similar to the QuietGround and 2 LB MLV options discussed above and also be very competitive in overall price as well.  The only drawback is if you add a second, permanent layer of sub-floor to your platform then it will become pretty difficult to move the platform if you ever need to.  If your platform is going to stay put for as long as you have it then this is of course not a problem.

Case Study

We had a customer in Minneapolis that likes to drum on an electric drum set in his apartment.  The only noise he really generated was the sound of the drumstick against the drum pads.  This sound was transferring directly to the neighbor’s below and he was receiving complaints about this.  So he contacted us to find a solution and the pictures below were taken by him showing what he had done and the final results.  Here is a quote from him about what he did and his results:

The QuietGround is working great!  I built a 5′ x 4′ platform out of 2″x4″s and a 0.5″ plywood sheet on top.  Since I didn’t want any of the roll to go to waste, I put two layers of the QuietGround between my carpet and platform, three layers on top of the platform, and some stock carpet on top of everything.

I have been rocking out pretty hard for some time now, and I haven’t heard a word from my floor neighbor.  I even contacted her and asked her to call me if there were ever any problems with the noise.  Still nothing!   I could have probably used less than 5 layers of the QuietGround to do the job, but I haven’t had any complaints so I have no reason to change the setup.  Thanks for the suggestion for building the platform by the way, I think that was key to isolating the sound.

Conclusion

Isolating sound transfer in a small area can be very simple and cost effective.  It also makes for a fun weekend DIY project–if you are in to that sort of thing!  With a basic platform and some sound isolation products beneath the platform and/or on top of the platform you will notice some dramatic results with minimal cost.  It is always recommended to treat the entire room rather than just the direct area that the sound is transferring through, but quite a bit of sound will want to flank through your floors so a simple platform will still reduce a serious amount of sound.

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Can Joist Tape Isolate Sound?

Not really.  Best case scenario if you were to add the tape to a 2″ x 4″ wall with 1 layer of drywall on each side you will find an improvement of 1 STC point.  This rating is based on an unofficial test performed by someone capable of performing a legitimate test and not just speculation.

Here’s the story for the test mentioned above and a pretty good summary of the world of joist tape sales:

A customer interested in finding an effective and affordable way to isolate sound on his projects contacted a seemingly reputable online sound isolation product provider.  They told him if he added joist tape to one side of his wall and hung just one layer of drywall then he would find an improvement of 10 STC points.  So he followed their instructions and applied the strip, then hung the drywall, and then sealed all the angles and joints with their acoustic caulk.  He ran some tests on his newly isolated wall and received results that provided an increase of 1 STC point.  So he called up the supplier and asked them why it did not work as advertised.  They let him know he needed to add the joist tape to both sides of the wall to achieve the 10 STC point increase.  So he removed the drywall from the other side, added the tape, hung some new drywall, sealed the wall, and ran a test.  There was no increase in STC rating.  He called the supplier and was only able to reach their voice mail and did not receive a return call.  He decided to drop it and moved on to using resilient sound clips in his projects.

Why Does Joist Tape Not Work?

If the tape is intended as a damper then it will not be successful as the tape has no damping properties and the foam material used to make this tape is not considered a legitimate damping product.  If the tape is intended to decouple the drywall from the stud then it will also fail as the joist tape is immediately shorted once the drywall is screwed into the stud through the tape.  So in terms of damping and decoupling, the joist tape simply does not have the ability to perform as a sound isolation product.

Are There Similar Low Cost Alternatives To Joist Tape?

There are some other options that will provide more benefit than joist tape for minimal cost.  The most basic option is using a damping glue on your studs or joists before hanging the first layer of drywall.  The damping glue most commonly sold for this is Green Glue.  There are no sound tests to support the claim that Green Glue on the studs and joists will provide a significant increase in isolation, but this is a method commonly spec’d on commercial projects and the concept is simple/logical.

You may be wondering why Green Glue on the studs would be better than tape on the studs.  The reason for this is because Green Glue is considered one of the best damping products manufactured.  Green Glue will effectively reduces vibrations between the contact of the first layer of drywall and the stud/joists.  Green Glue in no way attempts to decouple the drywall from the stud so the fact that the screw passes through the glue to the stud will not affect performance.  In fact, it will improve the performance of the Green Glue because it will help the Green Glue compress between the stud and the drywall.

Conclusion

Applying any product between your stud or joist and the first layer of drywall will not isolate a significant amount of noise.  Using a product like joist tape or integrity gasket will not provide any increase at all.  If you want to squeeze out a couple extra STC points from your isolation efforts then applying Green Glue to the studs is a real affordable way to accomplish this.  In the end though, decoupling and damping the entire wall or ceiling rather than just the studs is always going to give you the best bang for your buck.