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Sometimes,when I do tests or experiments on an RV gadget, it fails. Normally then, I just uninstall or don’t install whatever it is. Maybe I make a video about it, and maybe not. But in this case, where I had already made “Part 1” of the video series, and I couldn’t really uninstall it, there was no choice but to move ahead with “Part 2” and try to make the most out of it. This (long) video explains it all!
To recap – I tested the noise level on a test stretch of road to get a baseline. That baseline was 70.1 dB. Then, I tore apart the cab of the van, and installed the materials according to the methods I laid out in the last video. I reinstalled all parts of the cab, and then went for another 70 mph drive on that same stretch of road for an “after” reading. The results were disappointing, yielding a net drop of only 0.4 dB.
So basically, it was hardly worth doing what I did. But there’s value, even in failure
Determining WHY the result was disappointing was important to me. I could think of 3 possibilities. Either the materials didn’t work, I had screwed up installing them, or I just wasn’t measuring the right things in the right ways to notice any improvement. Figuring (or maybe just hoping!) that the third option was the most likely, I set off to do more investigating.
We weren’t at home, so I didn’t have access to that same stretch of test road. Nor did I have access to my shop. Nevertheless, I was able to come up with something using the thermal curtain that Winnebago supplies with the EKKO, that has – I think – pointed me in the right direction.
What I Learned
WHERE you measure the sound is important. If I had been soundproofing with the goal of making things more comfortable for the cat (12 inches off the floor)… then my soundproofing was a dramatic success! The cat now prefers riding in the cab, on the floor, even more so than the beds! But unfortunately, we don’t drive from down there, and our ears aren’t normally anywhere near there, so I didn’t get any kind of measurement in that area, and it wouldn’t matter if I had.
Too bad though, because the cat really seems to like it.
An RV Is Not A Car. Well obviously, right? But I neglected to pay attention to this simple fact when embarking on the soundproofing project. I followed a pretty traditional approach to automotive sound deadening. That had me treating the doors, the floorboards, and the wheel wells up to the firewall. In a car, that works well, because you’ll have covered about half of the area where sounds could be coming from.
But an RV is quite different. You sit higher, and there are giant open spaces above and behind where sounds can come from. I estimate that I only covered about 60 out of 360 degrees with my sound deadening treatments. This left a lot of untreated space all around.
Not only that, but RVs have structural elements (Cab-over areas, wing walls) that regular passenger cars do not. These extra bits don’t undergo the same level of wind tunnel testing that new cars do, so they’re hardly optimized for sound. But these areas can generate a lot of turbulence and hence, a lot of noise. Since these elements don’t exist in cars, traditional automotive sound reducing treatments don’t address them.
Above Is More Important Than Behind. This is one I wouldn’t have guessed. By creative use of the thermal curtain (just watch the video), I was able to determine that the area above the cab would be better to treat than the area behind the cab. Beforehand, I would have said it was a coin toss between the “forehead” and the back. Yes, the forehead faces into the wind and would take a lot of turbulence, but the back is fifty billion times bigger. But our testing showed that we were able to get more of a reduction by blocking noise from above than I was able to by blocking noise from behind.
Bear in mind that these results may well be particular to our RV. If you have a cab-over bunk, your results may be different. If you haven’t spent as much time trying to reduce rattles in the back as I have, your results may be different. If you travel with the vent fan open or the air conditioner on, your results may be different. Etc. etc. etc. If you intend to follow down my path, I really recommend you perform your own tests just to make sure you get similar results on a different RV.
So NOW What Do I Do?
Well, from our test results, it does seem like there’s something to be gained from applying sound reduction treatments to the forehead area and what remains of the original Ford Transit roof. I intend to do that, but only once we’ve returned home and I have access to my shop. That may take a while.
So there WILL be a part 3! (And, I can go back to my same stretch of road to test it!)
Any comments or questions, leave them below and I’ll do my best to answer.
We just bought an Ekko last week! Drove it home over 1,000 miles. Hanging the insulation curtain up while driving removes all the “bad noise” and makes it pretty quiet. We have some whistling from the tent canopy vent, we also seem to have noise coming in around the camper door as it doesnt pull closed tight enough and it does not appear that the door bolt can be adjusted. Also had a terrible squeak on the door latch that some foam tape temporarily fixed.
I also have a few other problems like a floor squeak where you walk in and a lot of cabinet latches that don’t quite work. Kind of disappointed on some of the finish but love the unit overall compared to toeing a trailer with a diesel 2500.
Circling back, as promised, to report on my new tires. I have a 2018 Transit (RWD) and replaced the OEM Hankooks with Michelin Agilis. The road noise is definitely less pronounced, though I didn’t take any scientific measurements. The biggest difference is that the ride is So. Much. More. Comfortable. I really hadn’t anticipated how much better the ride would be. Interestingly, at my normal running weight, the Agilis’ proper tire inflation is only 50 psi, vs 64/67 on the Hankooks. The lower psi is probably part of the comfort improvement, though I just think these are better, quieter tires overall. I realize that some Transit owners obsess over the fact the the Agilis have a little less rubber on the road and are very slightly smaller, but since RV tires age out rather than wear out, I’m not worried about the rubber and I suspect that the odometer runs off of the OBD, though I’m not sure. Regardless, the tiny difference to the odometer is not going to impact my eventual sale price. Really happy with the tires, both in terms of noise and comfort. Oh, and I left the stupid simulators (fake hubcaps) off. That may also be helping with the noise.
When it’s time to replace our Kooks, I’ve been thinking I’ll go with the Michelin. Glad to hear you’re having a good experience with them (and your comment makes me think about replacing ours early!).
I wasn’t aware that the Michelins are smaller. That’s odd. What size tires does your 2018 RWD take? Our 2020 AWD takes 205/75-16, and Michelin offers the Agilis in that size.
Is a Michelin millimeter actually shorter than a South Korean millimeter? That would be odd.
Thanks for this insight. I have looked at reducing the cab noise in our Fiat Ducato (aka Promaster) Motorhome. I discovered a company in the UK that has experience and makes kits for the Ducato. One part of their kit that you didn’t mention is an engine blanket. This is intended to reduce the noise coming through the hood and then the windscreen into the cab, and apparently that makes a huge difference. In my experience with a car, engine noise through the windscreen is a significant source, and my current vehicle has an extensive barrier on the underside of the hood. I, and others who live in hot climates, are concerned about the engine blanket and the effect on engine temperatures. So I paused the project for now.
Honestly, I don’t feel like I hear that much noise coming from the engine compartment, so I’ve not looked into it that much. Like you, I would be concerned about overheating the engine.
Thank you for all of the food for thought. About to try to reduce the noise in my 2015 Winnebago Navion. This gives me a lot to think about….also your wife is a saint and your cat is adorable!
The wife and cat couldn’t agree more!
Glad you found something useful in the video. Good luck with your project!
I didn’t read all of the other comments so forgive me if somebody already brought this up. I noticed that the cell phone did not appear to be decoupled from the tripod, or the tripod decoupled from the floor. I think sound/vibration especially in the lower frequency range is transmitted through the tripod to your phone.
Yeah, this was already brought up, but I dismissed it for several reasons.
See my response further down (August 9th) in the comments.
Speaking of noises – – the roof rack on my Ford Transit Connect howls at any speed over 60 mph, increasing with wind speed, until I tie my kayak to the roof. The rack noise disappears!
I’m theorizing that the change in airflow around the bow of the kayak extends to the rest of the rack as well. This suggests that small, strategically placed spoilers, or even strips of self adhesive foam placed in the airflow may disrupt the sound generating air waves.
If you’ve seen any of the whip antennae with the wire coiled around it… same idea. It works.
Sometimes, all it takes is disrupting the airflow.
or the kayak keeps the crossbars on the roof rack from vibrating.
When speaking of road noise, Vibration and noise go hand in hand, did the addition of air suspension reduce vibration and noise? I would think having air instead of metal springs holding up the chassis would greatly reduce sound transmission from the road to the vehicle.
Unfortunately, I didn’t take any acoustic measurements before and after the air suspension install, so it would be impossible for me to prove that out.
If anyone reading this is about to install air suspension though… this would be something interesting to test!
As Adam Savage says: “Failure is always an option”
And you know we love to watch your analysis, workshop tips and presentation regardless !
I have two comments re experiment design:
As someone already mentioned, I think your iphone might have picked up a fair amount of vibration ➟ sound from the ground coupling with the tripod. I previously played around with iphone dashmounts for video recording and was unpleasantly surprised by the very heavy induced vibration noise. You can test how much you are getting by doing a simple audio recording (or video and just listen to the audio)
Then drive another test with Stef just holding the phone in her hand and compare the audio recordings, I am willing to bet the amplitude of the induced noise is overwhelming any ambient noise you are actually trying to measure and reduce.
Second, I wonder whether you could save yourself some work by figuring out WHERE the most noise is coming from, if there is non-uniformity. Ie. from the seat head position or nearby, point in different directions. For example, I wonder whether the headliner plastic is creating more noise or the transmitted tire noise from below ?
As always, interesting, thought provoking, instructive and fun to watch – thank you both !
I responded to another comment somewhere about the vibration noise. I don’t think that’s the issue, for the reasons pointed out there.
(Basically, we already sort of did the test you mention, and there wasn’t any detectable difference.)
As far as where in the forehead the noise is coming from… I have to disassemble the whole thing to insulate any of it, so I’m going to just treat that whole area.
Thanks for watching!
James I watched your two videos on soundproofing the cab of the Ekko. Found them interesting and I think you need to do more research to reduce sounds. I dont have the Ekko but a Travato and didnt like all the road and air noise at freeway speeds. Here is what ive done to reduce the objectionable noise so far with good success (but not with before/after sound measurements). A lot of noise is air noise around the door. I added additional self adhesive foam around the perimeter. Helped some but needs more closed foam. Put Kilmat under floor mats especially the wheel well portion in the cab. Then I put Killmat on the outside sheet metal of the wheelwell where it is adjacent to the cab. That along with new Michelin Agilis crossclimate tires reduced the road noise almost entirely. It is as quiet as a passenger car. I still have wind noise from around the upper door which needs attention. But at least we now can listen to the radio and carry on conversation at freeway speeds.
I am also eyeing the Michelins for when we need to replace tires.
James, I noticed your dinette screen/shade system. Can you recommend the MFG that makes them? Have you done the bedroom windows as well?
It’s something we’re working on developing with an outside company. The ones in the video are the second prototype version. We’re getting close, but they’re not ready yet.
We’ll make a video announcing them when they are ready for purchase.
Just to say a huge thank you to you and all your contributors who have shared their actual experiences; so much more valuable that ‘expert opinions’!
I did a similar noise reduction project to a Promaster cab and once again the reduction in road noise was significant but in the end it really highlighted the wind noise. However, on balance, the reduction in low frequency road noise together with an upgraded music system with subwoofer made listening to music on the highway pleasurable and so the effort was worth while.
First: thank you for your amazing effort and time. Your comments on “who sucks” are really outstanding null hypotheses–kudos! The answer is YOU don’t suck at all. You’ve spent perhaps over 100 hours overall on this project. You and Steph are truly generous people!
There are many ‘hard surfaces’ in the EKKO…and the surface treatments there aren’t really very good at sound deafening, not to mention the considerable amount of exterior surface area combined with moving air that also generates noise. Some car manufacturers actually generate reversible (180-degree reverse wavelength) via the audio system. With multiple speakers in a car, this has proven to be effective but entails use of microphone(s) AND computer-generated software built in the vehicle’s sound system. I would think that applying materials to some of the interior surfaces might also help…but then the other issue then would be maintaining cleanliness. Last but not least: noise reduction or noise cancellation headphones. Caveat: this COULD be illegal in some/many/most/all states? But when used in the cabin of commercial jet aircraft, they are a WONDER! As long as no music is played, they can really cut down on the noise and should NOT defeat/cancel sudden noises such as a car/truck horn sounding. Your thoughts?
I don’t know about the legality of noise canceling (or any) headphones, and personally, I don’t think I’d like wearing them for an extended drive.
I do have some noise canceling headphones I used to wear on planes, but I think in the RV it might make me feel too isolated from Stef.
It works for some people, but I don’t think it’s for me.
Try this FIRST…before you rip out the ceiling…1)..Double up on the rubber gasket door seals..2)..Install a Fire Proof foam pad on the underside of the hood…I had a similar issue on my Subaru Ascent..I did the above and reduced the road noise by about 40%…The door gap seals on most cars are insufficient…The noise is also coming from the engine bay and through that thin metal hood,then transfers through the windshield and also the side windows….Sound is like a water leak.It’s never coming from where you think it is….That’s why luxury cars have sound deadening glass..A commercial platform like a Transit likely doesn’t….I had very good results just by adding extra rubber around the door seals..You can place sound deadening fabric over your cab side windows to test my theory..You can also add the extra rubber seal to that side entry door….https://www.amazon.com/gp/product/B0771T61VH/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 https://www.amazon.com/gp/product/B01N342LIP/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1….P.S..something as simple as taping masking tape around window gaps in your house will block sound intrusion tremendously,like passing cars on the street..Sound is AIR,so when you seal the gaps it stops alot of it..Try that in your living room or office windows…That’s why adding the rubber seals helps,it stops AIR and sound is AIR…
It is wisdom knowing and accepting that you failed. I have a Gemini built on the ford transit cutaway. the aerodynamics of the class C are terrible. It is my opinion that an active noise cancelation system will be more effective than hunting down the sources of the noise. I don’t know of an aftermarket one though.
You’re the second person to suggest such.
I used to consult in a call center that had an active noise cancelling system installed in the building.
I wonder if a room-sized unit might be adapted to an RV.
I likely won’t do it, but it’s interesting to think about.
Thanks for the comment!
I’m laughing uproariously at your sound challenges because context is everything.
We have a Mitsubishi Fuso cab-over camper. The turbo charged diesel engine sits between the two front seats. The truck itself is a 14,000 pound glorified landscaper’s 4×4 with maximum traction tires. We have plenty of first class sound deadening n the cab, but….. the war against road and engine noise is a lost cause. We just deal with it.
Our camper is a magic carpet ride to amazing end-of-road destinations. There are trade offs, no rig is perfect. We’re going to keep our baby, warts and all.
Oh trust me, I realize we could have it much worse on the noise front.
And if you’re happy with your rig, that’s all that matters! Enjoy the camping!
I’m curious what tires you are running. I have new KO2’s and they radiate noise through the front wheel wells like mad. The front’s have no noise abatement, so I am watching this thread in anticipation of some miracle. This is on a ’21 AWD.
That’s one of the reasons we don’t like the K02s. We’re mostly on-pavement.
We are still running the stock Hankook Dynapro HT tires. There aren’t many options here in the 205/75 r16 size.
It sounds like you need to pin point the location of the highest db levels and those are the areas to treat first. What about moving the mic around while driving to fine the loudest areas to treat?
I suspect your right about the aero issues from the RV box added to the transit chassis. Also, check near the rear wheels for tire noise from under the chassis where the manufacture might not sound insulate above the wheel wells.
Hi James, first time seeing your video and I like it! Have you considered suspending your pickup microphone(the cellphone your are using for measurement) so as to lower the floor noise contributed by the tripod?
Since you have already done the modification, we cannot have the ideal control condition. Still, I hope you can drive down the same road one more time with the microphone isolated from the floor noise and compare with your previous value. If there is a +ve difference, the % of noise improvement with your modification will increase significantly. Also, are you willing to provide your raw measurement waveforms/result? I am more interested in finding out the spectrum below 300Hz than the overall noise magnitude in your case. Thanks.
Glad you liked the video!
Interesting idea to work up an isolation mount for the microphone. Suspending it might be tough (it is a moving vehicle, after all). There is the option to use external microphones on some of the sound measuring apps – that would make it easier to use a regular microphone shock mount. Something to think about.
Bad news and good news on the raw data. The apps I’m using (NIOSH sound level meter and “Spectrum” FFT app) don’t actually record the data or the original sample. Nor do they provide a numerical or Excel output. They just do their thing in the moment. The NIOSH app will summarize things in a report, which you see in the video, but that’s it. I have some screen recordings of just the iPhone screen, but that’s not what I’d call raw data. And there are the recordings of the sounds, but they are colored (sometimes a lot) by the mics and recording equipment we used. That’s the bad news.
The good news is that the tests were no more complicated than you see in the video. There’s no magic there. The results should be easy enough for you to recreate if you have access to a Transit (or whatever vehicle you’re working on).
I was going to suggest this also. The mic in the phone used for the test isn’t isolated from its own chassis, which means any sound vibration from the floor is being transmitted (and likely amplified) through the tripod.
The tests in part 1 worked so well because the environment was so quiet and the sound was coming from a phone inside a box. The real world test is the inverse, sound outside the box being observed from inside where the mic is mechanically attached (via gravity) to the box.
I’m going to go on record as saying that the microphone mounting had a minimal, if any, impact on the results. Here’s why:
The tripod mount you see in the video is set on the cab floor.
In the “before” test, this mounting would have been on top of the rubber mat, which was directly on the metal floor of the vehicle.
In the “after” test, the tripod was on top of the rubber mat, which was on top of 1/8″ of mass loaded vinyl, which was bonded to 1/4″ of foam specifically designed to de-couple vibrations, which was on top of constrained layer damping material, which was then finally on top of the metal floor.
And, as you saw, virtually no difference was observed.
If there was any impact due to having the tripod transmitting vibrations from the vehicle, we would have seen something… ANYTHING… different in the after test. And yet there wasn’t.
I won’t be investigating this aspect any further. But if someone with an isolation mount, a Ford Transit, and a lot of time on their hands wants to prove me wrong… go for it!
Well, you just saved me a lot of pain and agony, so thank you. 🙂
Interestingly, some folks with Ford 350s and 450s have had a lot of luck sound deadening their doors and floors with Dynamat and the like, so folks with non-Transits shouldn’t assume the process won’t be helpful on their rigs. They should probably do some research on forums.
A few notes that may interest some readers: Coachmen ordered my Transit without the optional acoustic hood liner. I had a dealer order and install one and it made zero difference. Zero.
As others have noted, not running the air conditioner/heater on its highest setting dramatically cuts down on noise in the cabin.
The folks on the various Transit forums have decided the exterior mirrors are a major source of wind noise. Some owners on those forums have gone to enormous, highly creative lengths to try to lessen the noise, with zero luck.
James, since you have air bags, this won’t apply to you, but the two things that have helped reduce noise in my Transit were installing a Hellwig anti-sway bar and changing to Bilstein struts. I wouldn’t say it was a stupendous difference, but it was noticeable. I was surprised how much the anti-sway bar helped, as I hadn’t expected it and don’t completely understand why it made such a difference. I suspect the next big difference will be when I get new tires in a year or so. I’m leaning toward Michelins.
Thanks for all this work. I learned a lot watching the video.
Thanks! And you made some interesting points.
Those with vehicles with a “doghouse” will probably notice a lot of improvement from treating that. We don’t have one in the Transit though. So yes, if you have a 350/450, don’t assume this stuff won’t help much.
Didn’t know there was an acoustic hood liner available. And now that I know it doesn’t make any difference, I can forget about it. Thanks!
I think the mirrors may be a source of noise, but we’d have to do an A/B test with mirrors-in/mirrors-out to be sure. But even if I did know, I don’t know what I would do with that knowledge. It’s not like I’m going to delete the mirrors. Maybe a shroud?
Interesting that your suspension upgrades improved noise. My front suspension is actually untreated, so there may be something I can do there. I can’t fathom why that made a difference though.
Really good comments. Thanks!!
Hi James! Enjoyed this and many of your videos.
You may want to check out measurements with B and C weighting.
A weighting is used for OSHA measurements but significantly rolls off low frequencies.
Animals seem more concerned with low frequencies and you may have actually reduced more low frequencies…
I use C weighting for Music applications.
Check out these graphs!
Thanks for all your work!
P.S. You Do Not Suck!!
True, I could have used a different weighting. And it probably would have turned out a bit louder.
But, most of the material out there – including on exposure limits (which concerned me when pondering long driving days), as well as even the National Park Service generator standards – it’s all A-weighted. You would have appreciated the difference, but if someone wanted to compare my results to almost anything they might google, it’s all a-weighted.
You need to go through the seven stages of RV quietification:
1. Wow, it’s noisy in here
2. What? I can’t hear you!
3. Research the crap out of sound suppression
4. Waste a four day weekend taking apart the RV, putting sticky stuff everywhere, putting it all back together
5. Wow, it’s almost quieter up to 41 MPH
6. Sob uncontrollably for 15 minutes
7. Buy a diesel pusher
(But we’re not in the market for a diesel pusher yet.)
Best response ever!
Very interesting experiment. My guess is that the noise is coming mainly from the lack of smooth air flow like you mentioned a car is tested for. You should fold in your side mirrors at 70mph and see what happens, you’d be surprised.
Always enjoy your technical videos.
It would be interesting, and we’ll try it.
But I don’t want to drive around like that all the time!
1. In a muffler, which has actually no real sound reducing material at all, it works by simply blocking the roaring sound of the exhaust. One really small hole, a couple of mm’s, and you know it. Point is, 99% is a lot different from 100% in an install.
2. So to go after the 1%: It might be interesting to make a cup device–a mixing bowl with foam edges comes to mind–with the cell phone inside that you could actually pin point regions or areas of the floor and head liner that are noisy. I’m sure Stef wouldn’t mind driving while you crawl about on the floor and in the van…Maybe you can figure out why Mel sleeps in certain places.
3. one other thing, and you mentioned this at the very beginning of your videos, is the difference between a smooth and chip road, which you said you could easily distinguish. What is that noise level difference? Maybe that’s the best you can get. And maybe that chip road should have been the test.
The idea of crawling around on the floor with a stethoscope is interesting, but practically speaking, I just don’t think there’s much more to be gained there. The floor is actually quite quiet. It’s not as though I’m going to reduce the size of my bolt-holes in the Luxury Liner Pro from 1” to 3/4”, and suddenly a roar will become a whisper. That’s just not going to happen – it’s already a whisper.
But the difference in pavement surfaces is easily responsible for 4-5dB all on its own, that’s what we’ve found. It’s a large contributor. Cracked concrete is the worst. Next worst is chip seal. Asphalt is the quietest. Which makes me think changing the tires might make for a BIG difference.
There are tires that you can buy that are similar to the Tesla tires, the ones that have the foam inside. I think the reason Tesla did this is because the car has no ICE and the tire noise was really obvious and irritating.
Lots of interesting stuff if you Google “quiet tires”.
When it’s time to replace the tires, noise level is certainly going to be one of my criteria!
The nice thing for you you is that you only need worry about 2 of your 6 tires. The tires in the back probably don’t matter too much.
Re your comment that RVs are not air tunnel tested, we were driving around on the highway today (in our presumed air-tunnel tested vehicle) and I noted that the roar from accidentally leaving the max air fan open was more than any other noise in the van.
What with gas so high, it won’t be long before RV manufacturers will be air tunnel testing.
I would LOVE for someone with a low speed wind tunnel to let me put my EKKO in it. Still looking for the hookup there – if anyone knows anyone…
Love your experiments James! Sorry if you addressed this already, but did you consider the quality of the instrumentation you used for testing? Aside from considering the height of the placement, I wonder if you might have had a different outcome had you used a dedicated sound level meter? Either way, at least your “real feel” sense is that you improved things!
On a side note, as design and development coordinator in construction/real estate, I often work with an acoustical consultant. It always fascinating to learn how many factors can impact sound transmission: airborne vs vibratory sound, high or low frequency, how one frequency can affect another. Not to mention all the different tricks to isolate or deaden sound (sealing, deadening, adding mass and isolation through separation…). It’s hard enough in a building – I can’t imagine trying to do it in the cab of a vehicle with awkward, misshapen surfaces, where you have little to know room to work with and you can only impact such a small portion of the surface area.
I do have a dedicates sound level meter – old school from Radio Shack!
I’ve tried it in videos before, and it will give results that are consistently about 3dB more than the iPhone apps. But at least the results are consistent, and not random. That gives me the confidence to at least use the iPhone measurements to compare to each other.
Oh and if only I could use offset double 2×6 framed walls inside the RV….
Ha! Offset double studded demising wall is the best!
James, you just saved me a lot of time and effort. I did the storage cut out up top where the TV bracket was like you did and noticed the insulation in there. I had planned to take those panels down and add some sound deadening, but now I’ll wait for your results! One thing I did was make some covers for the three overhead compartments that go on with magnets much like the Van Made Max Air fan cover. I did that more for thermal isolation then sound, but it can’t hurt.
The magnet-on covers is actually a really good idea.
(Even if it wasn’t quieter or cooler, I still like things neat-looking.)
Have you thought about undersealing the front portion of your chassis. Check out this link: https://soundproofguide.com/vehicle-undercoating-for-noise-reduction/amp/
The nice thing about undercoating you will be able to spray a consistent layer and depending upon how your firewall is layed out you could apply a layer farther up the firewall. I also think the above cab treatment would also help.
Some RV makers, like Leisure Travel Vans, spray parts of the underside of their completed RVs with spray foam – both for insulation and noise control. But they only spray parts.
My worry with spraying the underside would be that there’s just so much… stuff… under there, that I’d wind up spraying some wire and permanently sticking it to the skin of the vehicle. I just worry about the potential for damaging something.
But it could be an interesting way to go.
But then again… 70 decibels isn’t THAT loud to start with! I don’t know how much I want to chase that.
I don’t mean to be disrespectful but a lot of times wisdom of some sort comes with age and I’m just an old man now but one of my favorite sayings of mine by me is this: Just because a person can do something doesn’t mean they should do something.
Funny thing about sound is it is no cumulative in other words one noise does not add to another to make a bigger noise. If you have a 5db sound and a 10db sound then you don’t have 15db of noise you have 10db. That makes it really hard to deaden noise. If you want to lower the sound you have to effect the thing that is producing the 10db.In my Rialta the floor and firewall are all heavily sound insulated. I am sure if I removed any of that insulation it would be really loud as compared to the just loud that it is now. My noise is wind and road noise and there is not much I can do about those sources. My point is you need to pinpoint the loudest source and work on squelching that. I would suspect that the things you covered were not the big noise items.
Agreed – as mentioned in the video, sound measurements in dB are not linear. Nor are they cumulative.
Hopefully, the sound coming from the forehead area is the main culprit. The testing would seem to indicate that.
I love that you have this here, since your YT comments are turned off.
Immediately upon seeing the first test I felt like I could see where this is all going to go The majority of noise is the lower frequencies. On one screenshot it showed the peak frequency @86hz.
My first assumption is the low end is more likely to be caused by vibration resonating through the structure. The upper harmonics are so much louder in the engine bay and under the vehicle, but the fundamental is resonating through the frame of the vehicle.
Looking at the overhead cap, a mallet/knock test of that cap, inside and out, while the spectrum analyzer is recording would be an interesting. If it’s got a lot of low end or a similar peak frequency, it would certainly be pointing you in the right direction although there just isn’t nearly as much you can do about dampening low end compared to upper mids and high end.
I believe that treating the cap can’t hurt, will help, but I don’t think you’re going to see a significant breakthrough until you can determine the source of the lower frequency noise and if something can be done about it.
I feel like I’m preaching to the choir here and I’m not telling you anything you don’t already know, but I still thought I’d share in case it might create a new rail for a train of though. Good luck!
Great as always. One thing you didn’t cover, which is a concern of mine, is the tinny sound the doors make when closed. First off, I have a Sprinter rather than a Transit so I get that there are differences before we start. But honestly I don’t feel my Sprinter is overly noisy (I will do measurements) but I do hate the sound of the doors closing. Did your work in the doors improve that? Petty, but still important to me
Second, we do run with a curtain behind us, primarily for temperature control. The fact that I can drive with minimal fan speed on heat or AC reduces the overall cab noise significantly. Noise is noise, right? Your tests have me considering enhancing the sound deadening/absorption factor of my curtain.
Anyway, great work and explanation of results. Looking forward to the next steps.
Some interesting stuff here.
First – yes, it did change the sound of the doors closing. But I didn’t think they were tinny sounding to begin with, so I’m guessing it’s a subjective thing on the sound. But the Constrained Layer Damping products are known to change the sound of the doors closing, absolutely.
I hadn’t thought of the curtain allowing a lower fan speed on the air conditioning. Clever!
If you’re looking to do something with the curtain, Second Skin Audio does offer some sound proof blankets on their site. Expensive and big, they’re meant for attaching to fences at construction sites. But I have thought of getting one of them and cutting it up to replace the curtain…
How about an active noise canceling system? I’ve heard of aftermarket ones you can use in your car and I’ve heard Elon talk about trying to put those in Teslas in the future.
James, You are a really good presenter. I like the way you’re able to provide technical information without it sounding like a lecture. But, sorry sir, Stef is still my favorite. 🙂
It’s OK. Stef is my favorite, too.
Humble Road (and others) applies his dynamat and heavy mass vinyl to the forehead tumor. The air hits that bulge over your head and can cause noise. Hopefully when you treat the overhead space that noise will lessen. Can’t wait to see because in a Winnebago Fuse (on a Transit chassis) we dislike the noise as well.
It’ll be a while before I get to try it, but we’ll see!
Since part 1 of this series, I’ve been thinking that the worst contributor to the noise are the front windows. Unlike my personal vehicle, in ford transit those are not acoustic windows and the let lots of sound in. I can tell it gets quieter in the Ekko when we put up the window sun-blocking material.
We also drive with the insulated curtain because I too noticed that it’s quieter that way. Glad to hear that it’s mostly the top part that provides this nice benefit!
Thanks for doing all the work on the insulation so that we don’t have to 😛
Do you feel it’s confining driving around with the curtain up? It just felt… weird… to me.
youre very thorough with all your hop ups. Looks like the happy medium here is the top curtain only instead of full. i like watching all your upgrade videos. you can open a business doing this stuff.
I don’t think Stef would let me work on anyone else’s RV!
Thanks for the great video. I can now save my time an not try to reduce the noise in my future Ekko. On a different note, I noticed that you changed the stock window shade/screen. The stock ones were really good. Why did you change the shade/screen?
We have a product that we’ve been working on with a manufacturer. More details will be available when it’s ready for prime time!
If Plan #3 doesn’t pan out we suggest just playing the first 3 Led Zeppelin albums through headphones. Road noise problem solved!
Andy & Kim
Hypothesis: Mel is sleeping on the cab floor due to the increased warmth and cushioning provided by the sound deadening material, and the change in sound is immaterial.
Hypothesis: Mel is sleeping on the cab floor because he wants to replace the fur that was under the mat and was removed by you 🙂 .
Well, on the second one… you may be right!
We had tried before to put cat beds and blankets and such on the floor there – he wanted nothing to do with them until now.
The professional videos I’ve seen they do butyl rubber products like Dynamat and Second Skin on the entire inside of the doors but they also do under the hood! You can actually buy rolls of generic butyl rubber. I know I’ve seen it on eBay in the past. You are probably getting a decent amount of engine noise at speed. If it were me I would pull the hood liner and replace with the rubber and also do as much as you can above the cab if that’s possible. Maybe try cover the doors in the rubber instead of the foam as well.
Well, I do intend to treat the overhead spaces.
Don’t feel like we’re getting that much engine noise though. The 10 speed turbo is pretty quiet. I don’t think treating the hood will get us anything.
And just as a reminder, there have been and will continue to be engine fires caused by incorrect or improperly owner-installed insulation in the engine compartment. Know what you’re using and doing. If in doubt, don’t insulate the engine compartment of a vehicle.