What is the best sound deadening material?

[Kartreana]

I have always bought the dynamat bulk packs but am curious if there is something better out there. I gutted my E39 touring interior for carpet and dash swap and stereo wiring and figure it's the perfect time to knock it out.

[klavender1]

I used this stuff in my truck and it works pretty well. A lot cheaper than Dynomat was. I have no experience with Dynomat so I have no comparison. Also Amazon shows unavailable now but you can get it from other vendors. I paid $40 for 50sqft.

https://www.amazon.com/gp/product/B012A ... UTF8&psc=1

[SlickDizzy]

FYI: Dynamat and similar products are not designed to block sound, they are designed to dampen acoustic vibrations. There is a difference! People who line their entire floorpan with Dynamat misunderstand its purpose.

For true sound deadening it is hard to beat mass-loaded vinyl over closed cell foam. When used properly with Dynamat/similar in places where it is actually effective, it can make a huge difference.

More information about effective sound deadening can be found here (good resource, worth some reading): https://www.sounddeadenershowdown.com

[gadget73]

^what he said. Dynamat does a great job eliminating that "closing the door on a beer can" noise but it doesn't do that much to really reduce interior sound levels. It does work nicely to close up small holes and gaps though.

[Shawn D.]

I really have to disagree with the premise that Dynamat does little to decrease interior sound levels. I used Dynamat in key areas on my 535i (the panel between the tail lights, license plate, rear valance, muffler heat shield, gas tank rock shield, rear seat floor pan, rear deck, and rear seat-bottom support bulkhead) and reduced the exhaust noise by about 1/3.

FWIW, after I did my typical obsessive research years ago on acoustic damping materials, I decided on Dynamat Xtreme. There's a high possibility of better stuff being out there now, but back then in $-per-effectiveness, the Dynamat Xtreme won. For the materials that actually listed their damping specifications (I ruled out using any that wouldn't publish specs), I created a spreadsheet (long since deleted) calculating damping per surface area per dollar and damping per weight. Dynamat Xtreme won on both counts.

[tn535i]

For true sound deadening it is hard to beat mass-loaded vinyl over closed cell foam.

We had a noisy machine here at work with pumps and such inside. Lined the door and sides the best we could with the above and it made a huge difference. I would argue that it stopped both reflected sound that otherwise would bounce around and escape the machine and the potential for those panels on the machine to act like a sounding board. We did not seal up any gaps or cracks with it.

My e28 has so much sound intrusion from the basic design of the window seals and the current gaps where they've separated that I doubt anything on the floors would make much difference. It might help with road noise but I think the biggest difference (bang for the buck) you can make in a car (any car almost) for road noise is probably your tire choice. Some are noisy and some are much quieter and I bet the differential in tire price (if changing them anyway) is certainly easier and less trouble than any sound treatment.

[Ordnator]

I agree about the impact tyre choice can have on road noise.

I fitted Goodyear Efficient Grip Performance tyres to the Diamantschwartz Eta back in 2015 and was so impressed that I also fitted them to the Zobelbraun Eta in 2017.

It is only a couple of db's quieter but a noticeable difference.

Regards,

Mick

[SlickDizzy]

I really have to disagree with the premise that Dynamat does little to decrease interior sound levels. I used Dynamat in key areas on my 535i (the panel between the tail lights, license plate, rear valance, muffler heat shield, gas tank rock shield, rear seat floor pan, rear deck, and rear seat-bottom support bulkhead) and reduced the exhaust noise by about 1/3.

Not sure if you were responding to me or the other poster but that is the crucial bit I was getting at - Dynamat-type products work best in key areas where panel resonance is a major concern. A well-placed tile on certain panels is often all you need.

Somehow this is misunderstood by many though, who waste the material going for 100% coverage on every panel they can. Once the resonance is stopped, closed cell foam and mass-loaded vinyl are MUCH more effective at actually "blocking" sound.

[vinceg101]

This is timely since I am doing the research for next year's interior swap-out for the M535i. For an E28 body, the biggest issue in terms of noise suppression/elimination are the doors and windows, specifically the joints and seals. In the older cars especially (pre-1986) there is a large, pretty thick vinyl coated closed cell foam mat across the entire floor under the carpet already and it hardly makes a difference it seems. In any solution to an E28 it is combination of a Dynamat-type product or liquid applied membrane and then an MLV product blanket.

I have bought a few things from these guys including their dbSniper MLV for the rear seat well and bulkhead over a Dynamat-like material when I upgraded my audio system: https://www.heatshieldproducts.com/auto ... insulation
This was it mid-install:

All that kind of made a difference, but without exact metering, it's hard to tell and may be just a placebo.

I have been tackling the interior environment from both a noise and heat problem; heat intrusion into the cabin (especially on long distance drives across the California Central Valley in July) is just as much, if not more, of a problem than road noise. Good products in smart assemblies can address both issues and will be how I approach my interior project.

For the OP, an E39 is light years more advanced and quieter than an E28, so there really isn't much you need to do (or likely can do) to make it quieter. As long as your door panels and seals are intact and you have quite tires as mentioned, they are very quite cabin environments.

[Shawn D.]

I really have to disagree with the premise that Dynamat does little to decrease interior sound levels. I used Dynamat in key areas on my 535i (the panel between the tail lights, license plate, rear valance, muffler heat shield, gas tank rock shield, rear seat floor pan, rear deck, and rear seat-bottom support bulkhead) and reduced the exhaust noise by about 1/3.

Not sure if you were responding to me or the other poster but that is the crucial bit I was getting at

I was responding to the comment "it doesn't do that much to really reduce interior sound levels."

[Mike W.]

It's curious how when I bought my E28 in '99, it seemed like a quiet car, which was in comparison to it's predecessor, a late E12. By the time I sold it 155K later, noise was one of the reasons.

I am of the opinion, without any factual basis, that mufflers get noisier as they age. I'm not talking about holes or anything like that, but the fiberglass packing, assuming it's still there, at least on E28 era cars, surely gets packed with soot over the years. How many years I'm not sure, nor the exact increase in noise.

I've thought about using or adapting E39 era vapor shields for the doors, an eighth or 3/16 of an inch foam has to be better than the ultra thin (if it's still there) foam on thin vinyl on E28s. While I don't have any road tests at hand that list db levels when E28s were new, I'm thinking they weren't noisy cars, so just restoring them to factory would work wonders. Mostly windlace around the windows, a brand new muffler, repairing/replacing any damaged/missing door seals and of course that big blanket on the dirty side of the firewall/tunnel area. There's more of course, the package shelf underside on E23s got much thicker insulation than E28s, Dynomat on the sunroof etc couldn't hurt, and I don't know which gives the best bang for the buck, but replicating factory isn't a bad start.

[sail_or_drive]

I am of the opinion, without any factual basis, that mufflers get noisier as they age.

And then there is this:




I wanted to look and see what an old muffler looked like so I cut this open. I still don't know what they really look like.

The car is much quieter with a new muffler.

I did not cut into the center resonator, but replaced it too.

[tn535i]

I have been tackling the interior environment from both a noise and heat problem; heat intrusion into the cabin (especially on long distance drives across the California Central Valley in July) is just as much, if not more, of a problem than road noise.

You got that right. Older BMW's are a bit of a green house to begin with but seem to leak heat or cool faster than new cars by far.

That muffler above looks like anything that was inside of it is now MIA.

[Mike W.]

I am of the opinion, without any factual basis, that mufflers get noisier as they age.

And then there is this:




I wanted to look and see what an old muffler looked like so I cut this open. I still don't know what they really look like.

The car is much quieter with a new muffler.

I did not cut into the center resonator, but replaced it too.

Interesting. What did it sound like, not quiet or noisy like a blown muffler?