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Wave Shepherd
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Back in the summer of 2017 I wanted to test a common rule of thumb: mass loaded vinyl should always be decoupled from nearby surfaces, and closed cell foam is the right material to do it.

Many of you kindly donated materials for this experiment and I am very, very thankful for it. I am thrilled to finally finish and post the results. This took a very long time to write because I did not have a solid method to interpret the results until just recently when we covered the transmissibility ratio in an acoustics class I'm taking. I apologize for the delay, but I hope the wait is worthwhile.

the report is at my dropbox here --> MLV decoupling report v1.3
 

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*proceeds to order 1 ton of pillow stuffing to market as my own decoupler*

Glad you got around to this. Thanks.
 

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Thank you sir, for taking the time to do the research, & saving me some time & money! :)
 

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Question. So what if the MLV can't hang free. Is it going to introduce noise? If MLV is used, without adding a dedicated decoupling material, and it is decoupled by trim panels and sheet metal, is that worse than no MLV at all?
 

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Thank you for this. I use 1/8" neoprene stuck to both sides with contact adhesive but now this has me thinking....
 

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Whoa. Good read. Thanks for putting in the effort.
 

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Is there actually a claim that using CCF between the MLV and door is done to enhance the effectiveness of the MLV specifically to block noise? I've never read that. Are there manufacturers/sellers claiming that?
I had always thought the intention of CCF between the door and MLV was to decouple to prevent any vibration/resonance of the MLV against the door panel...Which makes sense.
 

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From my research you need to start with a CLD tile with only 25% coverage( 2mm butenyl and 4mm aluminum gave the best measurements). Add a Closed cell foam as thick as you can find and place a mlv piece on top. Then apply 1" + inches of open cell foam on top. Each layer has an air gap.

Interior panel: CLD tiles applied to with 25% coverage, 3m thinsulate 600L as the final noise barrier.
 

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WOW, great report sir. Thanks for your time. Nice to see the heat wave pro I used with my MLV tested good. Shocked to see how poorly most of the foams worked for decoupling.
 

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Is there actually a claim that using CCF between the MLV and door is done to enhance the effectiveness of the MLV specifically to block noise? I've never read that. Are there manufacturers/sellers claiming that?
I had always thought the intention of CCF between the door and MLV was to decouple to prevent any vibration/resonance of the MLV against the door panel...Which makes sense.
ive seen claims of not decoupling causing the vibration from the car to just transfer to the mlv and cause it to not be very effective. dont remember if it is right from the companies, or some random diyma claim. I can see why it would be the case though.
 

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So, I don’t see what any recommendation might be. Is there a certain thickness of polyester open cell foam (pillow stuffing) that could be used to decouple, assuming we would only use in dry areas, such as under interior carpet, inside rear quarter panels, etc. How thick would this need to be before the MLV crushes it and renders it ineffective? Does 1lb sq ft vs. 2lbs sq ft MLV matter? Should we still utilize Richard Vedvicks method in the door and scrap the CCF MLV method? I obviously have more questions than answers, lol.
 

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Wave Shepherd
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Discussion Starter #16
Question. So what if the MLV can't hang free. Is it going to introduce noise? If MLV is used, without adding a dedicated decoupling material, and it is decoupled by trim panels and sheet metal, is that worse than no MLV at all?
A mass loaded barrier will reduce noise transferring from one side to the other. It could possibly introduce noise by rubbing/buzzing against a nearby surface if the conditions are just right, but generally not.

Is there actually a claim that using CCF between the MLV and door is done to enhance the effectiveness of the MLV specifically to block noise? I've never read that. Are there manufacturers/sellers claiming that?
I had always thought the intention of CCF between the door and MLV was to decouple to prevent any vibration/resonance of the MLV against the door panel...Which makes sense.
The two ideas you have are the same thing. Vibration of the mass loaded vinyl is transferring noise, no matter what causes it to vibrate. Manufacturers may or may not be claiming the decoupling works this way or that ... but manufacturers are catering to the idea by making vinyl pre-glued to foam or lead sheeting pre-glued between layers of foam etc. Decoupling using closed cell foam is also ingrained in the culture here for example see the next comment below \/

From my research you need to ... Add a Closed cell foam as thick as you can find and place a mlv piece on top...
My research shows otherwise. I encourage you to run an experiment with your approach and let us know how it goes!

So, I don’t see what any recommendation might be. Is there a certain thickness of polyester open cell foam (pillow stuffing) that could be used to decouple, assuming we would only use in dry areas, such as under interior carpet, inside rear quarter panels, etc. How thick would this need to be before the MLV crushes it and renders it ineffective? Does 1lb sq ft vs. 2lbs sq ft MLV matter? Should we still utilize Richard Vedvicks method in the door and scrap the CCF MLV method? I obviously have more questions than answers, lol.
If you squish a material to half it's original thickness, it will become twice as stiff (or more). If you use a vinyl that is twice as heavy, it can compensate for a spring that is twice as stiff. I did not investigate the ideal ratios to use because I consider it to be a narrow niche case and impractical for nearly everyone.

I believe the method of stuffing the door with absorbent material has some value and I did this in my build log before I learned of Richard's post. How much difference it makes, I'm unsure.

I guess the main case that was left untested then was:
N) MLV connected using Velcro?
Velcro itself has almost no spring-like properties since it is designed to be fairly rigid, so it would not help to decouple the vinyl if used with 100% coverage. However, I think you're suggesting use velcro to hang it on the edges and leave the rest of the vinyl floating which is the recommendation I tried to make in the conclusion. If the vibration along the edge of the vinyl is "far" away from the middle of the vinyl where it is floating, the vibration isolation is excellent.
 

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Thank you for this project, and especially answering our questions using your findings! You guys that do these experiments and objective comparisons make it much easier for the rest of us to chose equipment, materials, ideas to clone, and save a bunch of money. I, for one, certainly appreciate all of you knowledgeable guys helping out the rest of us!!!
 

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Thanks for your work and thanks to those that donated materials to support your work! It's great to see some scientific answers to our burning questions in this hobby.
 

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Wave Shepherd
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Discussion Starter #20
Thanks for your work and thanks to those that donated materials to support your work! It's great to see some scientific answers to our burning questions in this hobby.
Yes indeed, a huge thank you to everyone who donated materials for this experiment. We all sincerely appreciate the kindness!
 
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