Frost King and Duramat Hoodliner: Completely ineffective at reducing cabin noise

Intro
Back story: I went from 5 mile commute and putting 3-5k miles a year on my truck, to an 80 mile commute that is mostly interstate at 70mph. Aside from not wanting to aggravate my tinnitus, I felt as though I was having to turn up my stereo too loud to be able to hear it properly while at speed. It’s well known among motorcyclists that just exposure to loud noise for long periods can contribute greatly to mental and physical fatigue. So I did hours of research on how to decrease the noise level in my truck.


I decided on taking a risk with using Frost King duct insulation, since I so easily encountered forum posts from people that were pleased with the results of just insulating their doors. Here is just one example of a thread where people claim that FK works:
https://www.tacomaworld.com/threads/sound-proofing.388014/

My wife is disabled, we have a soul-crushing amount of medical debt, which is exactly what led us to move so far away so we can get super cheap rent. So, I don’t want to hear about how I should have used a product that costs 5 times more. I was forced to take the economy approach based on a healthcare system designed to make money for people that are already rich by denying care to people that need and pay for it. According to everyone else’s QUALITATIVE reports, I had every reason to believe the duct insulation would work.


Truck stats
It is important to list all of the possible contributors to wind, road, and engine noise on the test vehicle. As a motorcyclist, I’m pretty familiar with how seemingly insignificant projections can become a howling whistle.

2000 2.7L 4cly 4x4 with no mods, aside from a K&N air filter.
Standard cab with only small interior mods that should not affect noise.
BF Goodrich AT tires with retread
Bull bar on the front with LED light bar
Fender flares, OE
Vent Visors on the windows
Tonneau cover on bed, Extang fabric​

Methods
Insulating
I’m in the process of cleaning and refreshing my truck as it moves into its 19th year of existence, so I did the insulation in conjunction with other projects. Therefore, the order in which I insulated everything may have been backwards compared to others. Over the course of 7 months I installed Frost King on:
the ceiling
back wall
floorboards
doors
And Dynamat Hoodliner under the hood

$85 DYNAMAT 11905 Hoodliner 32" x 54" x 3/4" Thick Self-Adhesive Sound Deadener

https://www.amazon.com/gp/product/B00069QLVC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Below are the finished product of insulating each component. In some cases, where space allowed, I doubled or tripled the layers in order to help with point-sources of noise and/or heat, e.g. the middle hump through the cabin where the transmission is. I had to leave some areas bare in order to properly fit the carpet/panels that had to go over top of it. For the floorboards, I added as much as I could to the firewall facing the engine. I could get it a little higher than the carpet, but that still leaves a huge space behind the dashboard uninsulated.






Also note that installing insulation will result in lots of small pieces that are seemingly useless. I was so gung-ho about this sound damping that I even used these pieces and slid them into holes and gaps in places like the A and B pillars. You’ll also see that I even went through a LOT of trouble to apply insulation to the underside of the cabin tupperware, such as the parts that cover the:
A and B pillars
trim over the window
Cover over the seat belt tensioner
panel that covers the side in the footwells
Center console

In other words, I don’t know how much more I could have done.



Meter Readings
Tests were conducted with a sound meter I already had, which I bought just so I could learn the sound levels of various things for my own personal benefit. I have a science education and career field, but I claim to have no particular expertise in the science of acoustics.

$20 Decibel Meter, RISEPRO® Digital Sound Level Meter 30 – 130 dB Audio Noise Measure Device Backlight MAX/MIN, Data Hold Auto Power Off Dual Ranges HT-80A

https://www.amazon.com/RISEPRO-Decibel-Meter-Digital-Sound/dp/B01EZZ8B5Q/

• range from 30 – 130 dB with frequency range from 31.5 to 4Khz. Highly accurate with +/-1.5dB.

Results
I held the sound meter up at ear level, with my elbow resting on the lid of the center console and facing forward, which is roughly the center of the cabin. I took readings before I started insulating, and then after. Here are my results:

31 db - with the doors closed and nothing running (may possibly be lower, the sound meter’s lower limit is 30 db)

46 db - at a stop, engine warmed and at idle

66 db - at a stop, engine revved to 2200 rpm, the same as when going 70mph

71 db - at a stop with the engine on, fan running on high and circulate on

73 db - going 65 mph

75-76 db - going 70 mph​

Please note that understanding decibels is not easy. Every increase of 10 units of decibels is 10 times the sound intensity, but it’s not how we perceive the loudness of something. A change of 10 db is 2 times the perceived loudness.
https://www.noisehelp.com/decibel-scale.html
The following are readings that I have not yet measured after installing insulation.

While driving 65-70 mph, pointing the meter at various sources:

77 decibels at the door, in the footwell, windshield, side windows, rear windows

81 decibels at the rear wall (see more about this below)

For a comparison, a new 2019 Nissan Frontier read 67-68 db at 70 mph, but since it has a 5 speed the RPMs were lower at ~1900.​

Conclusion
After insulating everything listed above, the sound readings did not change. That means the insulation, both the Frost King and Duramat, had absolutely zero effect on the noise level in the cabin.

You can imagine my disappointment.

Note how the sound of the engine is a considerable source of cabin noise alone. 20 db is perceived to be 4x louder. I am disappointed even further that $60 for the top tier brand of hoodliner had zero effect on a considerable source of noise in the cabin. Unfortunately I am unable to isolate the sound of wind and my all terrain tires, since that would require getting towed at 70mph with the engine off.

In all of my research I never saw anyone posting a QUANTITATIVE review on sound damping that used Frost King. I don’t know how to explain all of the others that claim just slapping a few pieces on the inside of the door that cover only 25% of the area was effective (this is applicable to purposed made products, but I’ve seen Frost King used the same way).

Since people are susceptible to the placebo effect, I’m forced to believe that if I can’t get the intended results despite my exhaustive application of insulation (far and above what I have seen anyone else post), that others also did not get any positive effect. I suspect that since sound is not easy for us to quantify, and a comparison requires a memory of the conditions before the application of insulation, that people who claim it worked for them simply wanted to believe that it did.

You might be questioning the accuracy of the sound meter I used, and so have I. I don’t have a way to calibrate it to a known decibel level, but I can say the *precision* was spot on, since I got the exact same numbers with the truck stopped but with the engine running, 7 months apart.

What about phone apps? Most smartphone microphones are aligned to human voice (300-3400Hz, 40-60dB). Voice calls do not require high-performance microphones. I would like to assume this dedicated equipment would be more accurate that a phone app.


Continuing Work
I would like to discuss what I think is the greatest source of noise in the cabin. You can see my original thread here:
https://www.tacomaworld.com/threads/sound-damping-rear-cabin-vent.594886/

The highest noise readings I got in the cabin was pointing the sound meter at the rear cabin vents, up to 83 db, which is approaching a sound level is perceived to be twice as loud as the ambient noise in the center of the cabin.

I am no longer interested in trying to add more duct insulation. However, I think that trying to fix the noise intrusion from the cabin vents may be worthwhile and a last-ditch effort. I’m thinking of cutting out a few of the metal slats, perhaps the bottom 3 to gain enough access to stuff some type of insulation in there that would still allow the air pressure in the cabin to equalize when the doors are closed. I would welcome suggested on specific products that won’t hold moisture and can be squeezed and then expand.

 

When I had my interior apart I filled every hole in the body with expanding foam. It took 11 cans to fill up the cab with foam. I then laid down rattle trap mat.

It made a word of difference. Its no new car. But after 4 years of no interior, no floor. Only door cards a dash and seats it was a welcomed change.

 

I hope that works out for you. I also researched using expanding foam and there was an overwhelming amount of anecdotal observations posted on forums about it causing sheet metal to rust.

Proof
https://www.hotrodders.com/forum/using-aeresol-spray-expandable-foam-body-76526.html

 

Yep shot in the dark for sure. It my 2nd truck, the fun truck. So I figured it was worth the experiment.

 

If I'm not mistaken the door glass on a 97 is thinner then the glass on an 04.
@ThunderOne i believe went through this thinner glass before.
The mirror's are notorious for wind noise. I chased wind noise for months coming from the mirror area. Removed the mirrors and the noise was gone. Without an arrow dynamic mirror it's something you have to live with.

 

Correct, the older models have slightly thinner glass. Like less than 1mm. It was enough to make it rattle like crazy with the window slightly down on my 04.

 

I have always used this https://raybuck.com/product/jute-padding/.

I don't have dB meter to measure the before and after so is it an improvement for the floor carpet... don't know.

 

>>Since people are susceptible to the placebo effect, I’m forced to believe that if I can’t get the intended results despite my exhaustive application of insulation (far and above what I have seen anyone else post), that others also did not get any positive effect. I suspect that since sound is not easy for us to quantify, and a comparison requires a memory of the conditions before the application of insulation, that people who claim it worked for them simply wanted to believe that it did.<<
I think you are absolutely right.

 

also from what I've learned, most sound deadening material advises against "full coverage" and only to apply to areas known to cause the most "vibration" in the cabin (ex roof, floor, back wall)

and even then to apply in the middle of the spot as you cannot completely remove the harmonics only lessen.

but as you've found out it's the ambient(?) noises (wind, engine, etc) that cause most of the problem, and unless you research and design materials like higher end Lexus/BMW/Benz to combat these noises, it's a crap-shoot

 

My dude, that is a LOT of work and time you put into that for such little return.... That sucks bad.
So is it like Mechanicjon says and most of the noise comes from the mirrors? Wouldn't surprise me, I guess. Maybe I'll try a mirror delete just to do a test.
I do know that a couple months ago when I replaced my worn Michelin AT off road tires(yeah right, that tread is a road tire for most manufacturers lmao) for new Michelin LTX road tires the driving noise went down big time. So at least in my case, the noise created from the worn out tires easily made it into the cab.
Is it possible to move that decibel reader to different spots on the cab to see where the most noise is actually coming into the cab or where the loudest is measured?

 

Yeah, I just wasn't expecting it with so many accolades for Frost King I found on Jeep and Corvette forums. Like, WTF.

I did that already, and that's how I came up with the conclusion that the rear cabin vents being the loudest point in the cab. When I drive now, I can still clearly hear more noise from behind me than anywhere else, and that's with a double layer of FK on the rear wall.
I did the sound test for the entire cabin 7 months ago, but from what I remember pointing the meter at the windows was only slightly higher than the ambient noise in the center of the cab.

I have manual adjusting mirrors like the the image below. I could be totally wrong, but I would expect wind noise to be greater, or more likely, from parts that are thin, and not from this style that has very little seams.


I would expect to have problems with wind noise from something like this:

 

Believe it or not those are quieter because it moves the turbulence away from the cab.

 

What exactly are "those"?

 

You happen to have a link to those mirrors? BTW your high effort with little to no reward made my own blood boil, I wish you the best.

 

Heh, thanks. I hope that in the future this post will stand out to people doing searches and possibly sway them from attempting it.

I included an image of the same mirrors I have. I don't understand what you are looking for in a link.

 

So is there really any way to muffle noise coming from the rear vent window even though closed? I wonder if sealing off the window from the outside with something not permanent like caulk or something similar to seal up the transition between window, seal, and body panel. Basically trying to eliminate turbulence from forming around the window. I dunno, just throwing ideas out

 

The rear cabin vent and the rear window are two different areas. Although the window certainly allows noise in, the cabin vents that are the problem.

 

I like the design of the mirrors I was just wondering if you had a direct link to where their sold.

 

Oh the rear slider window? Ohhhh

 

Not sure how you'd keep turbulence away from there. Are the solid one piece rear windows any quieter? Anyone know? The slider is nice but the noise is brutal, especially since speed limits are going up and up which creates more noise and asphalt is being replaced by concrete on interstates which is waaaaay noisier to drive on as well