Killmat in trunk area = placebo

[GroovyGeek]

I was doing the subwoofer undelete today and took the opportunity to add killmat in the trunk area, see attached image. I had measured the dB levels with a phone app all week on my work commute and was measuring 68-70dB at 65-75mph on the freeway. After installing and putting the Bronco back together I took it on the freeway and measured 67-69dB. 1db is not perceptible so this was probably a measurement variance.

Having said that it SEEMED like I am hearing less road and tire noise. Since the noise with the MIC is dominated by wind noise it is possible that there is improvement but it is masked by wind noise.

Sas Broncos may see a bigger improvement since those 35s absolutely scream on the road.... at least that '21 BL sas I rented for a day a few month back was absolutely intolerable on the freeway.

YMMV

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[Ducati1098]

I’m curious if doing the top would make a difference. I remember seeing someone on here add kilmat or something, then reapply the factory top headliner over it. I can’t remember if they said it made any difference though.

 

[Rydfree]

1db is roughly a 33.3% drop in sound level .
Sound deadening is not the same as sound reduction/proofing.
Products such as KillMat/DynaMat reduce (deaden) noise and vibrations. You know, like the tinny sound metal makes when you slam the door.
A foam product will sound proof more than a layer of butyl rubber such as KillMat.
Different uses.

 

[VIRUS]

Had my daughter drive while I searched for a rattle in the back.

Seemed like a lot of sound was coming through the tailgate.

 

[Lcubed]

I was doing the subwoofer undelete today and took the opportunity to add killmat in the trunk area, see attached image. I had measured the dB levels with a phone app all week on my work commute and awas measuring 68-70dB at 65-75mph on the freeway. After installing and putting the Bronco back together I took it on the freeway and measured 67-69dB. 1db is not perceptible so this was probably a measurement variance.

Having said that it SEEMED like I am hearing less road and tire noise. Since the noise with the MIC is dominated by wind noise it is possible that there is improvement but it is masked by wind noise.

Sas Broncos may see a bigger improvement since those 35s absolute scream on the road.

YMMV

you really need to fire up a spectrum analyzer to see how well the treatment is working and over what frequency range. the dB number you're reporting is a wide band estimate over a large frequency range.

 

[John P.]

Yeah, with the tops on these things there’s not much benefit to this. Mass Loaded Vinyl would block more noise, but it’s still not going to do much.

 

[TonkaTruck]

1db is roughly a 33.3% drop in sound level .
Sound deadening is not the same as sound reduction/proofing.
Products such as KillMat/DynaMat reduce (deaden) noise and vibrations. You know, like the tinny sound metal makes when you slam the door.
A foam product will sound proof more than a layer of butyl rubber such as KillMat.
Different uses.

A drop of 1 dBA is barely noticeable to the human ear.

 

[GroovyGeek]

I’m curious if doing the top would make a difference. I remember seeing someone on here add kilmat or something, then reapply the factory top headliner over it. I can’t remember if they said it made any difference though.

Yes there is YT video on this. It was dynaliner + dynamat + reapply factory top. I am going to wait for someone to come up with commercial product and reviews with noise measurements. Adding the Killmat to the trunk was very little overhead since I already had it open for the subwoofer undelete. The MIC is going to be much more work.

 

[GroovyGeek]

you really need to fire up a spectrum analyzer to see how well the treatment is working and over what frequency range. the dB number you're reporting is a wide band estimate over a large frequency range.

Yup, I noted that it "felt" like I am hearing very little road/tire noise. But ultimately if it does not reduce the overall noise levels it is not worth spending the effort on. The Killmat costs next to nothing (1 box was sufficient) and the labor to install is not much if you already are opening the back for another reason.

I was always skeptical of people who claimed improvement because Ford does NOTHING back there when they add extra sound deadening with the lux package, and not I see why.

 

[Lcubed]

Yup, I noted that it "felt" like I am hearing very little road/tire noise. But ultimately if it does not reduce the overall noise levels it is not worth spending the effort on. The Killmat costs next to nothing (1 box was sufficient) and the labor to install is not much if you already are opening the back for another reason.

I was always skeptical of people who claimed improvement because Ford does NOTHING back there when they add extra sound deadening with the lux package, and not I see why.

without going into a long treatise, a large reduction in the lower frequencies may result in a very small change in the overall dBA level because of how the frequency weighting is done.

dBB or dBC is probably the more appropriate scale for the SPL levels in the bronco

this graph may help

 

[Rydfree]

A drop of 1 dBA is barely noticeable to the human ear.

Yes 1db alone may be barely noticible but 2 db ? My point still remains that sound deadening material is different and the benefits are in what it does do. If you want quite use something else. If you want to deaden the area for squeaks, rattles and the tinny sound of sheet metal then KillMat does wonders.

 

[Alassise]

That was my goal on my BL's (soft top)as I have a dual 8" down firing subwoofer on the back and the rattling on certain frequencies was a nuisance. To secure the sub in the back, I installed the Ford lid enclosure and it amplified the rattling as I expected. Installed the same killmat panels on the enclosure (back, lid and part of the sides, and exposed floor areas) and it truly minimized the rattling, the Bass sounds great. As far as road noise goes, the material is meant to attenuate vibrations. It does minimize the perception of road noise, but it won't make the Bronco a recording studio ever.

If I ever dismantle the back, I will do exactly what you did, I think that adding it to the doors will also benefit you to an audible difference, but again, all you might get is that closing the door thump similar to luxury cars...

 

[GroovyGeek]

Yes 1db alone may be barely noticible but 2 db ? My point still remains that sound deadening material is different and the benefits are in what it does do. If you want quite use something else. If you want to deaden the area for squeaks, rattles and the tinny sound of sheet metal then KillMat does wonders.

3dB is generally considered the smallest change perceptible to the human ear. The response of the human ear is logarithmic so 3dB is about 10% change is perceived loudness.

 

[Bellime]

I’m curious if doing the top would make a difference. I remember seeing someone on here add kilmat or something, then reapply the factory top headliner over it. I can’t remember if they said it made any difference though.

I need to take some pics of my foam modification that fits the sides under the mic which removes the noise.

 

[Bellime]

I took high density foam and trimmed it to fit. After confirming a snug fit allowing the top to be locked down I then wrapped the foam in Flex Tape. The noise next to my ears while sitting at any of the 4 seats doing 80 mph is greatly reduced.

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