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FWIW--I think the biggest contributor to road noise are your choice of tires . I am running Continental Conti-Pro 245/40 R18 on the front and 265/35R-18 on the rear, NOT run flats and the car is really quiet. For comparison my previous ride a BMW 535 with runflats was the noisiest vehicle I've owned.
What app and what iphone do you have? I used "decibel sound meter" on my iphone X and recorded my measurements at: 68-70db going 75-80mph on concrete freeway. 66-68db going 75-80mph on newer concrete freeway, and 64db going 75-80mph on smooth black asphalt freeway.
I used noico sound mat around my adblue tank in the truck (although not sealed edge to edge like I see in the pictures above), with some leftover uhaul packing blankets all around it and on top. I also used the noico sound mats under the back seat. I just bought a new 17" set of pirelli cinturato all season plus tires.
I still think my e250 is loud, but my previous car was a supercharged range rover sport with acoustic glass. I will say that it is definitely quieter than my wife's porsche cayenne with 21" wheels and conti dws tires.
What app and what iphone do you have? I used "decibel sound meter" on my iphone X and recorded my measurements at: 68-70db going 75-80mph on concrete freeway. 66-68db going 75-80mph on newer concrete freeway, and 64db going 75-80mph on smooth black asphalt freeway.
I used noico sound mat around my adblue tank in the truck (although not sealed edge to edge like I see in the pictures above), with some leftover uhaul packing blankets all around it and on top. I also used the noico sound mats under the back seat. I just bought a new 17" set of pirelli cinturato all season plus tires.
I still think my e250 is loud, but my previous car was a supercharged range rover sport with acoustic glass. I will say that it is definitely quieter than my wife's porsche cayenne with 21" wheels and conti dws tires.
iPhone X with 'Decibel X' app (all Software are up to date, FWIW).
Even though I blame the run flats on my 17" but still I got minimal results.
Anyway, that's just my experience. For other people who are starting this mod/upgrade, make sure you take readings as such for educational purposes.
DB levels have a something close to an exponential curve. Every 3 decibel increase is a double in sound volume. If you can decrease 1 to 2 decibels that would be a very good reduction in noise. Auto engineers give each other high fives when they lower DBs by 2 or 1.
Hello, sorry for my english..
I did an insulation upgarde for trunk area which resulted a noticable noise reduction for my sedan w212.
It is applicable for especially high/mid frequency tones which comes from rear side of car. Here are the photos: My spare tire, tire kit and trunk covers. Removed before installation. My tool bag and materials. 1st step installation of Insulation Material. "Oto Yalıtım 11". Made with polyester, self adhesive very strong, flexible. I noticed that the material is compact/intensive, 4mm thickness. Durable up to 110 Celcius. This is for high and mid freq tones.
1st step installation of Insulation Material. "Firex Foam". Self adhesive very strong, flexible, fire resistant with 20mm thickness. This is for low freq tones.
Hello, sorry for my english..
I did an insulation upgarde for trunk area which resulted a noticable noise reduction for my sedan w212.
It is applicable for especially high/mid frequency tones which comes from rear side of car. Here are the photos: My spare tire, tire kit and trunk covers. Removed before installation.
My tool bag and materials.
1st step installation of Insulation Material. "Oto Yalıtım 11". Made with polyester, self adhesive very strong, flexible. I noticed that the material is compact/intensive, 4mm thickness. Durable up to 110 Celcius. This is for high and mid freq tones. https://www.youtube.com/watch?v=pX_XEB2ZpEQ
1st step installation of Insulation Material. "Firex Foam". Self adhesive very strong, flexible, fire resistant with 20mm thickness. This is for low freq tones.
212 has its trunk insulated enough. You should start with the floor, from under the seats to the trunk. There is no need to insulate the spare tire, its door is good enough.