RV (Automotive) Sound Deadening Theory and Proof of Concept


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Here’s something that should surprise no one: Riding around in a noisy vehicle is miserable.  And since, as RVers, we spend plenty of time riding around in vehicles, it just makes sense to try to make our vehicle as quiet as possible.  In this video, which is the first in a two part project, I dive down the rabbit hole of automotive sound deadening, and come up with an approach to use on our Ford Transit based motorhome, a Winnebago EKKO.  Then, I try out my approach on a small scale to see how well it works.  Warning:  This video contains material that some viewers may find… educational.

 

First, for those of you who will inevitably say “just turn the radio up and it’s not a problem…”  Science and I disagree.  For example, the National Institute for Occupational Safety and Health (NIOSH) recommends the following exposure limits for noise.  Exposures at or above these levels are considered hazardous.

Time to reach 100% noise doseExposure level per NIOSH
8 hours85 dBA
4 hours88 dBA
2 hours91 dBA
1 hour94 dBA
30 minutes97 dBA
15 minutes100 dBA

It’s worth noting that we were able to achieve something greater than 85 dBA with nothing more than Stef’s cell phone.  So “turning it up” isn’t a great option, particularly not for long driving days.  And besides that, RVing should be fun!  Not “just barely below the level that will cause you harm.”  Right?  So, in my opinion, this is a project very much worth pursuing.

We spent weeks developing this video, and I don’t want to repeat everything that was said, so I’ll just hit the highlights here and give you links to the products I used.

 

Types of Noise

I broke down the noises we hear while driving our motorhome into 5 categories.

  1. Engine and Mechanical Noise
  2. Wind Noise
  3. Stuff In The Back Noise
  4. Road Noise
  5. Ed Sheeran

Of those, we’ll only be addressing Engine and Mechanical Noise, and Road Noise with this project.  The rest of them will have to wait.  And even for road noise, much of that comes down to your tires, and we won’t be doing a tire comparison in this series.

 

Approaches and Products

There are three different ways I’m going to try to deal with the noise in our RV, and I’ll use a different product for each.

Sound Dampening:  For this, I chose a Constrained Layer Damping product called Damplifier, from Second Skin Audio.  For the cab floor, wheel wells, and front doors in our Ford Transit, I ordered 40 square feet.

Sound Blocking:  For this, I used a Mass Loaded Vinyl product, that’s bonded with a foam layer for decoupling.  The product is Luxury Liner Pro, also from Second Skin Audio.  For the cab floor and wheel wells in our Ford Transit, I ordered 3 sheets of 9 square feet each.

Sound Absorbing:  These products are typically foam, and I used a hydrophobic foam from Second Skin Audio that they call Mega Zorbe.  For this project, I ordered a total of 16 square feet of the peel and stick variety.

 

The Proof of Concept

This was a resounding success!  I was able to achieve a 20dB reduction in transmitted sound by applying just two of the materials, the Damplifier, and the Luxury Liner Pro.  If I am able to get the Mega Zorbe into the mix as well, it looks like that’s good for another 7dB or so.

But honestly, I don’t think I will be able to achieve that in the vehicle.  The box I used in my proof of concept was a rectangular cube with flat faces, and it was easy to seal up all the sides perfectly.  Things won’t be quite so neat in the real world, where I have curves, windows, and moving parts to work around.  But that’s OK.  The proof of concept did let me know that the ideas do work, and the materials do work – which is good enough for me to move forward.

In the next video, we’ll see how much of the 20 or more dB of sound reduction I’m able to get in the real van.

Questions and comments down below!



James is a former rocket scientist, a USA Cycling coach, and lifelong fitness buff. When he's not driving the RV, or modifying the RV (or - that one time - doing both at once), you can find him racing bicycles, or building furniture, or making music. In his spare time, he works for a large IT company.


    34 thoughts on “RV (Automotive) Sound Deadening Theory and Proof of Concept

    1. Terry and Cindy

      It was so amazing to actually meet you guys at GNR. We love your videos and truly admire the time and effort you put into each of them. Today I use the TP your analysis determined best, I stopped wasting ice to clean my black tank, and even learned the virtues of 12v compressor refrigerators as you swapped yours in. Sound dampening is another project I have had on the bench, and am now eagerly awaiting your findings so I can dive in with highly reliable data and an understanding of what and why. When I said you are my idol, I was serious. Please keep up the amazing work and travel safe.

      Reply
      1. James - Post author

        I’m really humbled. Thank you!
        I’m glad our videos are helping out. That’s why we make them.
        We’re still working out the last of the second sound proofing video, so stay tuned.

        Be well and we’ll see you at next year’s GNR!

        Reply
    2. Jim Mohr

      James did I see the SOG Vent on the cassette compartment door in one of your recent videos. If so when will you be doing a YouTube video on the system. Thank you.

      Reply
      1. James - Post author

        Yes, we’ve had the SOG installed for a while now. I had been meaning to make a video, and then I sort of forgot about it. Thanks for the reminder!

        Reply
    3. Don Kane

      During our build, I noticed initially allot of air noise (and road noise and even traffic noise) from the back and the sides of the van. (Mind you, this is when a colleague of mine remarked that our van was the first vehicle he ever had been in that had an echo.) First big reduction was covering the floor with foam and minicel (and plywood and vinyl). 2nd, covering the back wheel wells. (That was a biggie) 3rd, insulation and walls in the sides/ceiling of the van. 4th, furniture attached to the sides of the van. Each of these steps was noticeable and reflected in how loud we had to turn up the radio.

      My biggest issue, and one of the ones that I think you have for the future, is tracking down and fixing squeaks in the back. Those are the worst. It will fun to share notes.

      PS, In regards to traveling with the wind, we were on a one tank trip going from Michigan thru Canada to Buffalo last month, and managed 20.1 mpg, our record for the highway. Sweet.
      Normally, more like 17.5 to 18.5.

      Reply
      1. James - Post author

        We do have significant wind noise as well. But as ours is a class C instead of a van, we’re somewhat limited in what we can do in the back.

        Reply
    4. Don Kane

      In our van (a simple Transit midheight midlength) we are quit happy with the normal highway noise. In our rig most of the noise seems from the wind. That is based no more than traveling with as opposed into the wind.

      The other major noise is from accidentally leaving the MaxAirFan open when on the highway, but that is quickly remedied.

      The only additional noise reduction we have in the front of the van are the stock Ford rubber foot liners.

      When traveling with the wind, the van seems really quiet, which means to me the engine and road noise are not a major problems, (although in bad roads we do suffer, I think that’s our non-air assisted truck suspension thing)

      Reply
    5. Don Kane

      It would be nice if there is some sort of sound insulated bucket (with the noise monitor in it) to test the noise leaked at individual spots in the cab. So you could figure out the loudest areas and focus on those.

      Reply
    6. Ian F

      Cool video. This is a subject I’ve been putting thoughts towards, although not to make my van more quiet (although being a 7.3 IDI diesel, I’m sure that will come), but actually towards my classic cars. And not just for sound, but also for heat. I have pretty much come to similar conclusions, but in addition I’m hoping to add heat shields between the heat-generating parts (engine, transmission and exhaust) and the body panels of the car. Having worked on a lot of modern cars with similar shielding, it will be interesting to see how successful I’ll be.

      Reply
      1. James - Post author

        I didn’t much address heat in this video, but I’m sure that will be a side effect of my project. (I hope!)
        We don’t have much of a problem with engine or exhaust heat in our Transit though. Our heat issues in the cab are mostly due to the glass.

        Reply
    7. Brian Nystrom

      I’m really curious as to what result you would get with just the Luxury Liner Pro, without the Damplifier underneath.

      Looking forward to the next video…

      Reply
    8. Kathy Stonesifer

      James, your posts are always inspirational! In this case, you have inspired my husband to finally do something about our noisy microwave using your methods – thank you!

      Reply
    9. Tsippi

      I used the same foam-backed mass loaded vinyl as you are using (Luxury Liner Pro) to cover my hollow RV steps. It helped very much. I put the LLP over two layers of a Dynamat-like product that honestly didn’t make that much difference in perceived sound. I have to confess, I found it almost impossible to cut the luxury liner pro. I couldn’t get the utility blade through it and ended up using shears, which didn’t give a neat cut. I don’t have your skills, nor your workshop. I was using a picnic table and am not very tall. Anyway, I’m hoping the next video may have some tips on making clean cuts, especially since, as you know, the stuff is very spendy — but worth it, in my experience.

      Reply
      1. James - Post author

        Glad you had a good experience with Luxury Liner Pro.
        I honestly didn’t have any trouble cutting it. I never even thought about it or even thought it was worth developing a technique. I just zipped through it with a straight edge and utility knife.
        If I had to guess, I’d say your problem was a dull blade in your utility knife. Most people don’t change them nearly often enough and the blades get dull quickly, and just mangle material.
        Get yourself a pack of 100 blades or so, and get in the habit of changing them for each project, or after 20 or so cuts. Yeah, you’ll spend 10 cents a blade, but you’d be amazed at the difference.
        Treat those utility knife blades like they’re disposable… because they are. 🙂

        Reply
    10. Michael

      Great video and content.
      I know the damplifier says to only cover up to 60% but then you also say mass is good.
      So it seems the damplifier is to stop the van panels from acting like a drum but wouldn’t it also be adding to the mass if it covered all of it. Plus would that stop sounds like talking in addition to road vibrations. Thinking of the back of a van.
      Additionally, I wonder if the mass of the damplifier would aid as a thermal break.

      Could you do a test with 100% damplifier and compare to the 60%?

      Reply
      1. James - Post author

        Well, the Damplifier won’t do anything for sounds that are already IN the van. So that’s a negative on the talking.

        And, since it’s miserable enough to take the cab apart and put it back together one time, I don’t think I’m going to do it twice to compare two different coverage scenarios.
        (You can try that one and let me know how it goes.)

        There IS some insulation value to the Damplifier. It’s nothing like the foam, or thinsulate, but there is some thermal benefit to installing it as well.
        That’s not the reason I’m tackling the project though, so I haven’t investigated that aspect.

        Reply
        1. Michael

          Sorry, I know that’s not what your goal is.
          I meant voices from the outside.
          I was just talking about testing your little box with full coverage.

        2. James - Post author

          Ah. I get it. That makes more sense.
          As far as talking outside the van… sounds are sounds. The material doesn’t discriminate based on the source, so yes, these methods would help with the sounds of talking as well.
          When I tested the box, it was quite a bit more than 60% covered. I don’t think it would have made much difference to go any further with it.

    11. Paul McPhillips

      Having a tiny bit of experience in Lockheed’s Anechoic chamber and building our van. A simple application of Soundskins Pro (arguably some of the best stuff) did the trick without the MegaNerd study. This stuff is quite expensive, we spent $1400.on the van and about $200.went in just the front doors. Problem Solved. yes we did the floor, ceiling, walls, rear doors too etc. The van was silent so the sounds of Led Zeppelin were studio quality. No Sheeran was allowed

      Reply
    12. John Williamson

      Just acquired a Storyteller LT, which is also based on the Transit. STO did a really good job of making the “build out” part quiet and pretty much rattle free. HOWEVER, I was really disappointed with Transit chassis part, with regard to noise level. Of course the KO2’s don’t help, and w/o doing SPL tests, I think most of the noise is coming through the sheet metal surrounding the front wheel. Ford applied an “undercoating” to the rear wheel cavities, but nothing except a plastic liner on the front wheel cavities. I don’t notice that much noise coming from the rear, and I attributed that to the undercoating plus all the “build out” surrounding the cavities.
      I can deal with some engine noise, but the drone of the rubber hitting the road is no fun. I’d bet that you’re getting a lot of sound generation through those front wheel wells, but you’re going to tell me that in a later video. 😉
      You produce a stellar vlog, and I thoroughly enjoy your content.

      Reply
    13. Jacques

      Kudos for doing the video.

      I would love to see the Fourier transforms before and after, superimposed. I imagine that some of the products you are using may be decreasing the high(er) frequency noise FOR lower frequency. Measuring the integral above or below certain frequencies may be more informative; after all, lower frequency noise is pretty annoying (think sitting at the back of an airplane). Best of luck with the project and keep tinkering!

      Reply
    14. Denis (Advanture 001 on instagram)

      James, you are a real “NERD” Sir, but I understand what you are saying and doing, even with your white noise, db meter… Does that make me a nerd also. Love the T-shirt Steph!!!LOL… So roughly 30 dbs lost with your reverse aquarium, in your Ekko, my guess is that you can lose about 20 dbs of road noise and mechanical noise by dampening the floor and the doors. PS please check your instagram, messages.

      Reply
    15. Kevin Scarbel

      Dynamat……tested and proven. Nothing better. The leader in sound isolation, and noise and vibration reduction (NVH).

      Reply
    16. Michael Yates

      Just when I thought my mod list was getting near the end, you add a big one to the top of the list. When my wife and I travel, it tends to be to one of the coasts or a national border. We live in Minnesota, so those are long trips. In just over four years of ownership. we’ve put about 65,000 miles in our RV. Our number one complaint now that we have our RV almost perfect is the road noise. I cannot wait to watch the subsequent videos because I will be a fast follower on our Era. btw here is a list of mods off the top of my head that you MADE do:
      lithium batteries – check
      hydraulic stabilators -yup
      roof fairing – u-huh
      removed 3rd seat and built a cabinet including shoe storage – you betcha
      roof storage box- got it (I know you did it on your bike rack but potato = potato)
      beefed up suspension – saw it on das Bus
      and there are others….
      Please keep up the great ideas, not only are they entertaining, I put them into action

      Reply
    17. Adam

      Was once an intern while in school for Mechanical Engineering, and worked on a project to silence, or as near as can be, an in-home medical product that contained a very noisy air compressor.

      What I learned

      1. Sound-deadening foam is likely to cost a lot of time and money (and take up a lot of space) with very limited success. For a start, deadening with insulation is only really useful if you have deadening material at least as thick as 1/4 the wavelength of the offending sound, AND
      1a. Deadening with insulation requires you seal up ALL openings between you and the source of the noise. A remarkable amount of sound can come through a small opening.
      2. Attacking the problem at the source (noisy tires? Get quieter ones) is 10x more useful than trying to insulate (see 1, above) the problem away
      3. Vibration is also sound. Abandon all hope ye who enter here.
      4. Perceived sound level is logarithmic. Take away half the sound pressure and you’ll only get a 6db change. Which is to say, if you’re measuring your success on the dBA scale, it’s easy to get discouraged.
      .
      Seems like there’s more, but now I’ll watch your video.

      Reply
      1. James - Post author

        1a, 2 (somewhat) and 3 are covered in the video.
        Didn’t specifically explain #4, but yes.

        Reply
      2. John Williamson

        Noise at the source…totally. I suspect in this scenario that the constrained layer damping will have the most benefit, and use up the least space.

        Reply

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