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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.