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Discussion Starter #1
I love the Elise, but I value my hearing, and well earplugs kinda get uncomfortable. So for the past month or so I have been researching how to most effectively decrease the noise level in the cabin. Well today was the day to put the theories I had read to the test, and though I have a ways to go even now the difference has been profound.

Essentially, there are two things you need to control to make a car quieter. First is resonance, which is vibrational based sound transmission. The second is creating a sound barrier to airborne sounds.

I stumbled upon an interesting tidbit about controlling resonance, essentially you can eliminate a large amount of resonance by only covering 1/4 of each panel in the center. The product for this is something like Damplifier or Dynamat. I used damplifier.

The second part is sound barrier, which requires some sort of vinyl mass with a decoupling layer usually a foam layer. For this I used Luxury Liner. Now luxury liner is heavy at about 1.25 lbs/sq ft but for relatively little coverage the sound improvement has been substantial.

With that background here is what I have done so far.
1) Damplifier on aluminum firewall behind driver seat covering about 1/4 of the driver side panel.
2) Luxury Liner under drivers seat
3) Luxury liner covering the aluminum firewall portion on both drivers and passengers side.

One nice feature of luxury liner is that is is modestly rigid so I just sat it in place, no adhesive required, but I do plan on adding some Velcro to the pieces covering the firewall so they won't sag with time.

This is as far as I have gotten so far. Even with only this much covered, the noise reduction is substantial. I can hear the radio well, I can talk on my phone (in fact my wife said she could barely tell I was driving), and I can actually hear cars next to me passing by. The one downside is I can now hear some squeaks and creaks from the dash area the til now I was unaware of.

I plan to take this even further and pop the door panels, install a strip of Damplifier and a thin lightweight sound insulation foam. I also plan take down the back trim panel add strips of amplifier them apply luxury liner. Based on what I have achieved so far I expect the end product will be completely transformational. Added weight so far had been right at about 5 lbs, and I expect by time I am done it will add 12-15 lbs. But well worth the 1-1.5 hp lost.

I'll follow up with pics and impressions once I get more done.
 

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Discussion Starter #3 (Edited)
Loud sounds for prolonged periods can cause hearing loss. People are not machines so there is no specific engineering tolerance that are globally applicable, but OSHA requires workers exposed to sound levels over 85 db to have hearing protection because of hearing loss risk.

The Elise is loud, and OSHA standards are felt by many professionals to not be conservative enough. I do know that the Elise is loud enough to me to feel discomfort, which is a sign of hearing loss risk.

Stock exhaust has been measured by s111 at 70-101 db (idle to redline). Remember that a 3 db increase is a doubling of intensity since db is a base 10 system meaning +10 db = 10x, +20 db = 100x, +30 db = 1000x intensity.

http://www.sector111.com/images/products/product_comparisons/exhaust_comparison.pdf

These measurements were taken outside the car, and I will look to see if I can find comparisons to see about sound inside the cockpit, which may not be improved because sounds resonate through the body panels well, but even then if the sound outside is 101 db then the sound inside is going to be loud too given the near zero sound insulation.

But, really it's a matter of personal preference. Many find the Elise loud and would like some modest noise reduction, some want every 0.001 hp they can get and strip every oz away they can get. To Me a few extra pounds for a more comfortable ride is well worth the minimal performance hit.

But, currently I have not measured the sound with a meter yet, but hope to get the chance to do that. One nice thing about the luxury liner approach is that I did not have to use any adhesive for the parts I have done so far and it can be installed or removed in under 5 minutes. So if I can get a meter I will snap some measurements. Subjectively the improvement is substantial. I was able to hear my radio through out my drive at 1/2 the normal volume level I had it at in the past.
 

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Discussion Starter #6 (Edited)
I'll take some pics today.

If anyone does this, I way overordered supplies. Sheets of Luxury Liner come about 4.5 x 2 feet. One 9 ft sheet of luxury liner is more than enough to cover under drivers and passengers seats and up the exposed aluminum portion of the firewall; a fair amount of this is wasted from trimming up the pieces. A second 9 foot sheet would be needed to do behind the plastic trim panel.

Covering only 1/4 of the panels with Damplifier, a little goes a long way. So far i've only used about 1/4 of one sheet. But plan to use about 3 sheets total. Need to remove the seats to apply the Damplifier, the luxury liner can slip under the drivers seat, but the passenger seat sits lower and must be removed.

Speaking of which is it possible to install the adjustable rails from a driver side seat on passengers side?

And just so I am not misleading anyone. So far this has decreased the drone and decreased the noise level substantially, but don't expect BMW or Lexus near silence. Although I'm hoping once the plastic trim piece on the firewall is covered that sound levels will drop even further.

Admittedly, this is ultimately hopefully a 3 steps forward one step back project since part of my motivation is to quiet the car so I can add a slightly more sporty exhaust. Crazy, maybe but at least I will be back near stock weight between the two upgrades. But, even then I hope it will be much quieter with a newer exhaust than the stock setup.


 

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I would like to see pictures to psoup. I'm thinking the same thing. I wouldn't mind a lighter exhaust, but the wife won't like it if the car is any louder inside than it already is.
 

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Doesn't a hard top reduce the noise?
 

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Discussion Starter #10
Doesn't a hard top reduce the noise?
I don't have a hardtop, so I can't speak to that, but the hardtop should only help reduce ambient outside noise and exhaust noise coming in over the top, but the most direct route for noise is through the firewall, plus with the metal panels is is a bug setup for resonance.
 

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Psoup, does your car have the foam baffle behind the rear bulkhead? My purist does not, and no carpeting anywhere either. I plan to add carpeting, as well as follow your mods, placing dynamat or similar on floor and rear firewall under the carpet and behind the rear bulkhead before installing the foam. I had thought about the door panels as well, so interested in your approach, and I will also be adding leather covered dash panels, and rear bulkhead, etc. which I hope will quiet some squeaks, as well as add some sound absorption.

I know others are cringing, but as a daily driver in the northeast, these small additions can make a big difference.

I am very interested in seeing your pics, especially the front footwell/firewall area. I am also thinking about the side sills underneath what will be carpeted (runs only half way up, but still), as well as underneath the side sills (also adding these in leather, but I don't think there's much clearance underneath. I believe dynamat comes as thin as 1/4 inch). Can you also post your sources for damplifier and luxury liner?
 

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You know, I was thinking about this earlier today. People who are "complainers" should not own a elige. :D
If this is all you came up with after a session of "thinking", then I am underwhelmed. Sound levels in the Elise are high -- that is a fact. For those of us that are lucky enough to drive one every day, year round, noise exposure is a problem. I wear earplugs for any drive over a few miles. This is not a complaint, just acknowledgement of the fact that the Elise is loud. I would love to make it a little quieter and I appreciate the content of this thread, most of it anyway.
 

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You know, I was thinking about this earlier today. People who are "complainers" should not own a elige. :D
You excel at subtlety! :rolleyes:

Seriously, these cars are great BUT there are some shortcomings. Any reasonable person knows this.

Does anyone have a stock elige? Everyone is doing some mod. Guys that put different exhausts are complainers? Guys that don't like the plastic carpet buttons and put the aluminum thingies on are complainers? Guys that paint the center console are complainers?

Seriously dude, nothing wrong with trying to enhance the comfort and driving experience. For example:

- the AC in my car absolutely sucks (non-existent). Am I complainer because I didn't feel like sweating profusely on 92 degree/95% humidity Chicago summer days?

- Am I complainer because I had more foam added to my non-Probax seats when I had them reupholstered?

- Am I complainer because I upgraded my stereo because I would prefer to listen to Iron Maiden as opposed to exhaust drone when I drive for 2 hours?

Engine/Cabin noise is a big deal in these cars. I'd imagine the spouses/significant others of many of the forum members would echo that same sentiment. I see nothing wrong with trying to minimize the noise a bit and increase overall driving comfort level (and reduce fatigue).
 

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Sounds interesting! I am looking forward to hearing updates about the end results.

I have been playing drums (not quite as long as SwingLo) for years, so I am partially immune to loud sounds over prolonged periods ;), but wouldn't mind quieting down the cabin.
 

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Discussion Starter #16
Psoup, does your car have the foam baffle behind the rear bulkhead? My purist does not, and no carpeting anywhere either. I plan to add carpeting, as well as follow your mods, placing dynamat or similar on floor and rear firewall under the carpet and behind the rear bulkhead before installing the foam. I had thought about the door panels as well, so interested in your approach, and I will also be adding leather covered dash panels, and rear bulkhead, etc. which I hope will quiet some squeaks, as well as add some sound absorption.

I know others are cringing, but as a daily driver in the northeast, these small additions can make a big difference.

I am very interested in seeing your pics, especially the front footwell/firewall area. I am also thinking about the side sills underneath what will be carpeted (runs only half way up, but still), as well as underneath the side sills (also adding these in leather, but I don't think there's much clearance underneath. I believe dynamat comes as thin as 1/4 inch). Can you also post your sources for damplifier and luxury liner?
I honestly don't know if I have the foam baffle or not, I have not pulled the plastic cover to look yet. Hopefully soon.

Dynapad should work well too, it is a little different design basically foam-vinyl-foam instead of foam under vinyl, otherwise they are pretty much the same thickness...There were a couple reasons I went with Luxury Liner over Dynamat, one was because at least in the short term I did not plan on covering it and the vinyl on top instead of foam top should hold up better at least I can wipe dust off it easier. My second issue with dynapad was that there are logos all over it, and since I planned to have it exposed uncovered for the time being didn't want it to look unfinished.

Dynapad is more expensive than Luxury Liner, which honestly had nothing to do with my decision which way to go, but if you are looking at saving a few $$, the Luxury Liner is the cheaper route.

From reviews I found the second skin audio products were pretty much on par with the Dynapad products, the major difference for me, no logos and marginally lighter weight.

Sound Deadening Materials for Noise Reduction from Second Skin

For anyone wondering, I have no affiliation with second skin audio, the fact that they are from AZ is just serendipitous...just happens to be what I used, and I would love to hear someones results using the Dynapad products (supposedly you can remove the logos with acetone).
 

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I don't have a hardtop, so I can't speak to that, but the hardtop should only help reduce ambient outside noise and exhaust noise coming in over the top, but the most direct route for noise is through the firewall, plus with the metal panels is is a bug setup for resonance.
Hmmm. I'd be curious to know the db level with and without the hardtop.

I thought for sure the hardtop was described as "noise reducing" due to the insulation.

Can't wait to see the pics!
 

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Discussion Starter #19
Pictures so far.

So here are some pictures depicting the basic setup.

The piece on the firewall needs some more trimming for a better fit, but it fits pretty snug right now as it is.

I will create a separate post with the supplies list for what was used, but one correction I used Luxury Liner Pro, not Luxury Liner as originally stated. Luxury Liner (non-pro) is a thicker but heavier vinyl with no decoupler foam (you add the decoupler separately).

And to just clarify, essentially how I did this was to measure the spaces using a tape measure (it's pretty simple geometric shapes), cut the product outside the vehicle, then just slide it into place.
 

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Discussion Starter #20 (Edited)
Parts List

Sound Deadening Materials for Noise Reduction from Second Skin

Luxury Liner Pro 18 sq feet ($80)
Damplifier 4-8 sq feet depending on if you do the doors ($16-32)
Overkill Foam 9 sq feet if you want to do the doors ($15) -- I have not done this part yet so 9 Sqft may not be enough, so u may want to but extra. It's light at like 0.16 lb Sqft.

Shipping cost me 29.00, but I ordered about double everything listed here.
And if you are in AZ, you'll pay tax.

Other items you may want, which I also purchased
High Temp Spray Adhesive 1 can ($18)
Wooden Handle Roller (helps to smooth the Damplifier which is pretty stiff) $15

I'm also toying with adding vibration dampening areas (Damplifier) to the fiberglass body panels, but I don't know how much sound is really transmitted through fiberglass by resonance.

You could do pretty much the same thing with the dynamat line.

-- Dynamat Xtreme = Damplifier (Spec wise I like Damplifier better, your aluminum constraining layer is 6 mil in stead of 4 which should be better, and even better would be damplifier pro but it is 2x the weight at about 0.6 lb/sq ft so I thought I would just double the damplifier if I wanted more dampening)
-- Dynapad is Similar to Luxury Liner Pro (Dynapad is a 4 way sandwich, I liked the idea of the LLP a bit better since you have a thicker decoupler under the vinyl which should isolate better from the body panels, or so it seemed to me)
-- Dynaliner is Similar to Overkill (I like dynaliner a bit better because it has adhesive on it already, but I was ordering from second skin audio so I bought the overkill, may still buy the dynaliner because the adhesive may be a PITA to try and get installed inside the doors)
 
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