maxcooper

I want to make my FD quieter. I know there have been some good threads about door treatments, brush on stuff, etc. This thread is about my quest to make my car quieter.

Tonight I did a baseline test so I can track progress.

Test conditions:
I chose 80 MPH on cruise to keep things simple, and because that is my normal highway travel mode. I watched the Radio Shack dB meter for a while to see how sensitive it would be to the type of pavement, and I was pleased to find that the readings were pretty stable, varying only about 1-2 dB A or C as I cruised down the highway for a while. If I changed lanes and hit lane markers or bumps, the sound level would jump, but for the most part it was very stable. It didn't seem to matter much where the meter was, either, at least between the various places I could hold it with my arm while driving. The readings were much more stable than I expected. I'll use the same stretch of road (405S between Jamboree and Jeffrey) with similar traffic (pretty light, but still cars around, ~11:15PM Sat night) to gather comparable results in subsequent tests. Enough chatter, here are the results:

A-weighted, slow, Radio Shack meter: 82 dBA
C-weighted, slow, Radio Shack meter: 102 dBC

Links:
My bushings thread where I started talking about this: https://www.rx7club.com/suspension-wheels-tires-brakes-20/musings-bushings-399866/

A good thread about some brush-on sound dampening stuff (also with tests):
https://www.rx7club.com/interior-exterior-audio-26/quietcoat-sound-dampening-195306/

McMaster-Carr has some basic info on their site, too, which seems like a decent layman's introduction to the various types of sound control materials:
(drat, unlinkable site , go to catalog page 3270 at http://mcmaster.com/)

I got some info from an automtive NVH expert, and the tip was that hot water heater blanket material makes a good absorber, that "shower barrier" stuff makes a good barrier, and that an absorber-barrier-absorber sandwich does a great job at keeping noise levels down. So that should explain some of my Home Depot material choices below.

I'm trying to do this cheap (a sure way to overspend and have lots of extra useless crap left over ), so I've gathered the following materials so far:
1. McMaster-Carr part #9709T19, adhesive-backed mastic
2. McMaster-Carr part #9709T25, 3-ply aluminum stuff that has a better DLF number while being lighter and still cheap, probably easier to apply, too, as it is easy to mold into whatever shape is needed.
3. 3" thick hot water blanket from Home Depot (absorber to use in spare tire well, perhaps stuff in empty spaces [was: body cavities, but then I realized...])
4. Thick vinyl shower curtain liner from Home Depot. I think this will work pretty well in an absorber-barrier-absorber sandwich, but I guess I was supposed to get some stuff that you put in the walls around a shower well instead.

I still need to get some thinner hot water heater blanket (yellow with the foil backing) and some "shower barrier" instead of the shower curtain liner I got.

I think I'm going to try some dampener in the hatch area or inside the doors next and then re-test. I'll try to re-test often and between procedures, but it's likely that I won't be able to test each change individually. I am also working on some exhaust and other changes, so I will be sure to note those changes here and hopefully re-test each one. Exhaust drone is one of the major contributors to the noise level, so I'm hoping to reduce that with a Magnaflow in the midpipe.

-Max

maxcooper

Got some "shower liner" and the thinner hot water heater blanket today at Home Depot. The shower liner stuff is $5.29a foot (5 foot wide) and is 40mil versus the 6mil shower curtain liner stuff I got before. It should be much better.

I just stuffed the rear cargo divider with the thin (1") hot water heater blanket and the 6mil vinyl shower curtain stuff. It's fits pretty easy -- just cut to shape and sandwich the divider back together. The screws just poke through the stuffing.

I'll dB test it tonight. I don't expect much change, but at least I got started with something.

I also got a little "corner roller" thing to assist with the mastic installation. It is a tool for wall paper installation. I got the heavy duty one with the wooden wheel. $6 at Home Depot.

-Max

moehler

iTrader: (12)

Nice... I'm very interested in how this will turn out .

maxcooper

Tonights test with the cargo-divider change:

A-weighted, slow, Radio Shack meter: 81 dBA
C-weighted, slow, Radio Shack meter: 101 dBC

The meter seemed to be reading a little lower this time, though I suspect that 1 dB is overstating the results a bit. When I first started driving it seemed quieter, but the sound level was not noticably different on the highway. I think I need to add some warm idle tests, too.

I am going to put the mastic down in the hatch floor area next. And then put a thick absorber-barrier-absorber sandwich in the spare tire well.

Tonight I heard about an interesting technique to pinpoint the noisy areas. Drive around with a passenger and have them listen to different areas to see where all the noise is coming from. A stethescope can be helpful, or even a little funnel at the end of a hose. Or you can just put your head close to stuff and listen, but it's probably easier to pinpoint areas while driving with the stethescope or funnel.

I also learned a bit about tuning the resonance out of an exhaust system. I guess you want to have different lengths of pipe between each component (muffler, cat) rather than, say, 3 ft - cat - 3 ft - muffler. I am not sure how my exhaust currently measures, but I think I will check that out. Also, you can calculate where along the exhaust path you can put things to kill a certain resonance, but I don't quite understand the math for that well enough to post about it yet.

-Max

maxcooper

Warm idle tests:

A-weighted, slow, Radio Shack meter: 64 dBA
C-weighted, slow, Radio Shack meter: 86 dBC

-Max

vchacon

perfect! I've been putting off my black interior conversion because I want to lay down some sound deadening material, I just didn't know what? I look forward to the results...

BTW, if you need any help on the weekends with anything let me know.

prew

iTrader: (9)

i have been wanting to do this for a long time too. you should weigh the car now, and weigh it when you are finished to see how much stuff you have added.

teeter

something I noticed the other day...

the door side intrusion beams inside the door are a "long" way (1 inch?) from the actual door skins. And the factory puts HUGE gobs of tar in there to tie the door skin to the door beam...presuably to reduce noise. Well...in a car I was working on...the tar had all fallen down into the bottom of the door. Literally fist full sizes of tar in the bottom of the door...doing nothing but adding weight

another car I had worked on...some previous owner had stuffed styrafoam(?) and rags inbetween this beam and the door skin.

IMHO...a robust way to tie the doorskin to that beam might help in reducing road noise coming through the door skin. I'll be doing it

john

maxcooper

I've heard about that issue, but I haven't taken a look for myself yet. I didn't realize the blobs of goop were so massive.

-Max

rynberg

NO! Wrong conclusion to the problem. Bridging the exterior panel of the door to the interior panel in that way will only allow noise to more readily transfer to the interior.

The tar serves as a damping compound for the exterior door skin, and THAT is what reduces the noise radiated by the door. The solution to this is to reapply damping material to the door skin.

You can see the effects of this yourself by trying a simple experiment. Find a bell, a crystal glass, a cookie sheet, etc. Strike it and listen to the "ringing" of the object. Now take a piece of putty or some similar material and apply it to the object. Strike it again, and now hear how the sound is quieter with much less sustain of the sound. This same phenomenon occurs with your car. Given the nature of 10+ year old automobiles, the most effective way to reduce noise in the FD will likely be the damping of the body panels, and not adding heavy layers of "barrier" products.

teeter

Thats what I meant. by saying "robust " meant that you wouldn't have to go do it again in 20k miles when the tar fell out again. I was thinking of stuffing something tar like in there...and then using the tar/foil backed stuff all along the bottom to "hold" the crap up in the door...or maybe glue the shower barrier(40 mil stuff) in there so it held? Bet emblem glue would work wonders to glue that barrier stuff to metal...

Thats all I meant. I realize welding or other more solid ways would make it noiser.

john

cmartinp28

i dont know if this make any diffrence to your study but i just bought 120sq ft of dynamat type rubber material with aluminum reinforcement for 99 dollars

ill keep tuned, maybe i can use some of the tips that you are comparing

potatochobit

iTrader: (1)

the door areas make the biggest difference in regards to road noise i think.

teeter

icaat

http://www.carpages.co.uk/lotus/lotu...echo=540450282

lotus is working on it...not sure if there will ever be a aftermarket version. if there is...oh yah...i'm gettin it

john

DamonB

I lined both the backside of the door skin itself as well as just behind the door trim panel on the interior of the door. Made a huge difference.

pianoprodigy

I have three layers of Dynamat extreme in my doors. Two on the outer door skin and one on the frame/vertical portion. The doors sound much nicer when closed. I have a lot of resonance from my exhaust though in the cabin. I wish I could get rid of that. I have a Magnaflow muffler welded into my midpipe. I imagine that has something to do with it.

pianoprodigy

I have three layers of Dynamat extreme in my doors. Two on the outer door skin and one on the frame/vertical portion. The doors sound much nicer when closed. I have a lot of resonance from my exhaust though in the cabin. I wish I could get rid of that. I have a Magnaflow muffler welded into my midpipe. I imagine that has something to do with it.

cprx7

I did my doors today.. spent about $35 at home depot. I used the stuff used by roofers. It comes in a roll that's 30 feet long I believe and about 6" wide. I used about 2 1/2 rolls for both doors, the inner skin and outer skin. It's made a big difference, specially in the highway. I have no idea how it compares to dynamat.. but for the price it's damn worth it.

artowar

iTrader: (1)

How much weight did it add to your car? Does it stink when it's hot?

cprx7

Each roll must weight about 6-8 lbs and I used about 2.5 rolls.. that's 15-20 lbs total between both doors. I could have probaly used 1 roll per door, but I was a bit **** and added double layer in some areas. The stuff doesn't smell. It looks just like Dynamat... it's self adhesive (peel off paper on the back) the front of it is aluminum foil to reflect heat away supposedly. I just installed it today and it hasn't been hot so I don't know if once it warms up it'll smell. I'll be a nice change from the exhaust smell if it does though

maxcooper

I coated the hatch area floor tonight. Though I was still skeptical that the 3-ply aluminum stuff from McMaster-Carr was twice as good as the heavier mastic, I decided to start with the aluminum. It isn't easy work, but the aluminum stuff goes on pretty easy. It stretches enough to fill in the ribs in the floor, it holds it's shape once you form it, the surface is very tough and you can use the handle of the roller to mash it around without any fear or ripping it. I really like this stuff. Here's a picture:


Unfortunately, that's all I had of that stuff. I should have ordered at least 2 sheets. I continued with the job by switching to the mastic I got from McMaster-Carr. This stuff is harder to install, though it is still relatively easy. It stretches, but it springs back to shape a bit. The adhesive isn't all that great, either. These two properties made it tend to pull away from the bottom of the ribs. It is also a good bit thicker, so it's best to have the sheets butt up to each other. In contrast, it was no problem to have some overlap with the aluminum. Here's the hatch floor after all the damping materials were applied:


I did a little panel banging on the areas I covered with the aluminum versus the mastic, and while I can't say I could make any specific determination of relative damping abilities from this test, I am starting to believe that the better DLF number for the aluminum might be true. I also noticed that the recessed area where the spare tire normally goes is a lot more "live" than the raised areas of the floor. Perhaps I should have started from the bottom of the spare tire well with the best material and worked my way out. I also wonder if having the spare tire in there helps to stiffen up that area.

Before I was done for the day, I made an absorber-barrier-absorber snadwich to fill the spare tire well. Each slice is roughly 25" round. The hole doesn't look all that round, but I guess it is an optical illusion, since the pieces ended up nearly round when I was done trimming. I started with a piece of 3" thick hot water heater blanket from Home Depot. I also cut out a hole in the middle of this one to make space for the raised part in the middle. Then I cut a circle of 40mil shower barrier, also from Home Depot. And then finally another layer of 3" hot water heater blanket, this time with no hole in the middle. I just stacked them up in the hole with no adhesive or anything. Here's what it looks like, with the layers peeled back to reveal the construction:


I then went out and did my usual test run. Here are the results:
A-weighted, slow, Radio Shack meter: 80 dBA
C-weighted, slow, Radio Shack meter: 100 dBC

I tried to do a warm idle test in the Del Taco parking lot, but I got 65 dBA, which is up one from my last test. I think some ambient noise or proximity to other objects (cars, walls) messed up the test. I will do another warm idle test before I make any more changes.

For both changes I have made so far, I am down about 2 dB total. It isn't much, but the car actually seems quieter, particularly after today's changes. It would be nice to have a more comprehensive set of tests (with better accuracy and precision), but I'm too lazy for that.

I'd like to remove the sandwich from the well and do another test, but I bet any difference would be below the amount of error in my measurements, since the difference was only ~1 dB for the whole shebang.

-Max

maxcooper

So, after today's changes I was pretty convinced that I should order some more of that 3-ply aluminum stuff for the doors. It is easier to work with, lighter, and has a better DLF number, and it doesn't seem to cost all that much more than the mastic stuff (well, actually it is $2.52 per square foot, versus $1.22 for the mastic, before shipping costs).

Before I ordered any more, I decided to do some price and specifications comparisons. I looked at Dynamat, B-Quiet, Fatt Mat, and eDead. eDead is pretty inexpensive, but I couldn't find any specs. FatMat has good prices and it seems like they might have good products, but the web site is a mess, the only specs I found weren't good (though I suspect they are wrong), and it is heavy. Dynamat Xtreme looks good but is expensive. So I ended up ordering 50 sq ft of B-Quiet Ultimate. It was $2.40 per sq ft versus $2.52 for the 3-ply alum McMaster stuff I liked, and with cheaper shipping than McMaster-Carr. It is also lighter at 0.35 lbs per sq ft, versus 0.4 for the 3-ply aluminum.

My hood liner is ratty, so I also ordered some B-Quiet Hliner stuff. I am hoping that will turn out to yield a decent sound reduction as well as simply looking better than my torn up stock hood liner. I also ordered some B-Quiet Vcomp barrier stuff, to perhaps use in the doors, under the seats, on the firewall, etc. The total with shipping was about $250. So much for being cheap, but after comparing the specs I think this stuff is better, and considering the time it takes to install, I want to make sure my time will be well spent.

Dynamat has a Dynaplate product that it claims is the best stuff they offer. In two layers, it damps as well as their Xtreme product and weighs less. It sounds very similar to the McMaster-Carr 3-ply aluminum stuff, though I am sure it isn't precisely the same. The McMaster-Carr 3-ply aliminum is made by SoundCoat (as evidenced by their logo on the adhesive backing sheet). The SoundCoat web site doesn't have specs, but is says they can make the aluminum sheet stuff in several different configurations. The 0.21 DLF on the McMaster-Carr site isn't directly comparable to the specs from Dynamat, but it seems to be in the ballpark. Myabe I should have just ordered more 3-ply aluminum and doubled-up with two layers. It sure is nice to install.

-Max

potatochobit

iTrader: (1)

is the bquiet stuff the same as the brown bead stuff? i was thinking about getting some of that.

maxcooper

They don't make the Brown Bread anymore, but they say that B-Quiet Ultimate is better.

-Max

rynberg

Sounds good, Max. Soundcoat does a large business in the industrial and commercial areas and their products do work. Keep us updated.

BTW, your photo taking skills are improving....no blurry shots, no feet, and no sasquatch!