Dynamat and other ways to quiet a noisy car?

I spend far too much time in my car. It's a 2012 outback and my sales route has me on the road 60-200 miles a day, and a couple of the days include a lot of time on the highway. After an hour or so I can really start to feel the effects of road noise, so instead of buying something new I want to try to quiet this beast down.

How effective is dynamat or generic alternatives? What I've read is a little helps a lot, and more helps a little more, correct?

Doors - does it go on the inner frame, on the inside of the outer metal door panel itself, or both?

Under the carpet and head liner - how does it hold up to moisture and sitting in ice all winter long? I'm thinking under the drivers and passengers seats, footwells front and rear, under the rear seat, and in the hatch area (sides and spare tire well).

How much area should I be covering? Just lay down a 12"x12" square on each spot?

What else can I do to quiet things down?

Dynamat will help some on panels that can resonate and transmit noise (like the door skins). It doesn't take anywhere near full coverage to make a difference.

If you really want quiet, you want to coat every possible bit of metal (floor pan, etc.) with a layer of closed cell foam (as a de-coupler) and then something like a mass loaded vinyl to absorb the sound. For this stuff, effectiveness drops fast as you get further away from 100% coverage.

Car audio sites usually have a few people floating around with good knowledge on this stuff, so a little searching around there might produce a good guide.

Any air leaks are huge noise leaks also.

A square on a large panel (e.g. door) makes a huge difference. Putting a square in the middle of a door on an old car has a dramatic effect.

The primary difference with Dynamat from what I have determined is that it will likely stick a bit better in very cold or hot situation. It is WAY more expensive then some other options, so if you want to save a bit, getting some glue for the alternatives is a good idea.

I am not sure about a 2012 outback though. I would think it would be pretty quite already. Road noise means tire noise which means mostly floors and firewall (if you can fit a square in the door that would probably help a bit also). Your question about floors and moisture is a good one. I would guess if you plan on getting it wet you would probably want to put some sort of undercoating type paint over any patches. I think people normally just rely on good floor mats and / or drying out the carpet when needed.

One way to test if the floors are a source is to get a bunch of laundry / blankets and fill up the car floors with them (obviously be careful with the drivers floor). I would suspect a new car would likely not have a lot of big panels that don't already have some sort of deadening (what dynamat is most useful for). Just putting a layer of jute under the carpet might have a good effect (see laundry test above).

Shameful truth: I like sedans nowadays because wagons are too noisy.

I used cheap eBay stuff called FatMat on my s13. It was waaaaaay cheaper than Dynamat, but a bit thinner. That wasn't a huge problem because it was still cheaper to double layer the FatMat than single layer the Dynamat. My only complaint was that it didn't stick as good as the expensive stuff. I ended up using a heat gun to get it tacky, and that worked better, just time consuming.

All said and done, it made a world of difference in that car. Less squeaks, rattles, and road noise.

First, thump test the panels. If it resonates, it gets dynamat. (I use McMaster carr mastic as a much cheaper and just as effective solution. Just requires a heat gun and j roller for install to make it stick good)

After the thump test comes higher frequency noise. Panel resonance accounts for the lower frequency.

I typically use foil backed jute for this. Bug rolls from home Depot are the most economical solution, though not necessarily the highes quality or most effective. Very little difference between it and the good stuff, but home depot is thicker. May be important in application. I aim for 100% coverage of the floor, firewall, and roof with it. Glue it down.shiny side towards the metal.

On top of that, for heat and cool purposes, i use a layer of the foil bubble wrap that lowes sells in the insulation department. Works well, and thin. This mar also act as a decoupling layer, not sure. But i glue it down as well.

In tbe doors i use a layer of 1/16 or 1/8 closed cell poker table foam with the bubble wrap glued to it duct taped where the factory plastic vapor barrier is as sound deadening and insulation. Really does a good job, and the door is still serviceable.

This all costs me around 150 per complete car. Makes a HUGE difference in hvac performance, interior noise, driver fatigue, and stereo system quality.

Honestly, my 3 inch exhaust equipped 70 duster is as quiet inside as my brothers 16 tacoma.

Hope this helps.

I used Frost King insulation from Home Depot...the silver closed-cell stuff. It works well at a fraction the cost of the car-specific stuff for like 90% of the effectiveness. Also very lightweight.

When I was researching, it seemed to be a favorite trick of Corvette guys to quiet things down. YMMV.

This is relevant to my interests. Please, do continue.

As far as I can tell the outermost layer needs to be panel damping if applicable, then a decoupling barrier - usually closed cell foam, and finally a sound barrier such as mass loaded vinyl.

Some sound deadening learnin' here.

I'm not sure I'd do it on a newer vehicle that wasn't already in pieces, but Lizard Skin is pretty cool stuff.

I just did Noico (see ebay) sound deadening in my 2010 silverado. Did each door with approximately 5 sq. ft. of sound deadening each. The difference is remarkable. At highway speeds the truck interior would have a hum from road noise, now the main noise is wind. Pretty amazing.

I applied the sound deadening by cutting it into 10-12in strips and putting inside the door.

I'm a bit confused here. This is a 2012 car. To be honest, I find it very hard to believe adding some aftermarket bits designed for marginally improving comparatively loud classic cars is going to make much of a difference against what the factory already did.

Is the problem road noise, driveline noise or wind noise? There are different approaches to each problem. Unfortunately, wind noise is the most difficult to deal with.

What kind of tires are you running? Some brands/models are noticeably more quiet than others.

Dynamat never worked wonders for me. Seemed like a lot of money and weight for not much benefit.

I'm trying to come up with some solutions as well. One thing about sound is that it doesn't like to change amplitude or frequency. Dynamat works best with low frequencies because it basically adds weight and dampening to a panel that would otherwise passively respond to higher frequencies.

So, in finding ways to dampen sound, look for dense and not-dense together. Like a layer of light, closed-cell foam backed with a denser layer of cardboard or foil. The noise has to change to make it through the foam, then change again to make it through the denser layer. Forcing it to change is one of the keys.

Also curious on the tire situation. Tires make a huge difference in road noise based on my experience.

Tires are Cooper CS5 Ultra Toruings, about half worn. I don't think it's mostly tire noise, as it's been about the same between these and my blizzaks. I'll probably wear these out by the end of summer, so I'll tackle the tire side then. Recommendations?

Drivetrain is stock, and quiet. I actually wouldn't mind a bit more engine noise lol.

It's road/wind noise I'm trying to combat. Around town is fine, but over 60mph things get loud, almost a dull roar, in a hurry. I added window visors at the end of last summer which helped with some of the wind noise, but wind is definitely a bit part of it. I usually set my cruise at 75mph and have to really crank the radio to hear over the road.

Even nice new cars could often be a lot quieter. The current CAFE bogeys are, uh, ambitious and every system on the car is fair game, including weight. The prevalence of electric power steering instead of hydraulic is an example -no one switches to electric because it offers superior feel or feedback. When I bought the Accord one consideration was it was quieter than the competition. Truth be told there is still room for improvement and at some point in the future she will get additional sound reduction, in part because I'm getting older and road noise is more fatiguiging to me than it used to be. Now get off my lawn!

You don't happen to have a roof rack do you?

It seems most folks use dynamat incorrectly. I place part of the blame on Dynamat's marketing. About 20 years ago the installation instructions stated to not cover more than 40% of a panel, and that any more was a waste of product. Someone realized they could sell a lot more by deleting this info, then internet forums popularized double and triple layer installs.

This person isn't quite aware of how the product works.

This is laughable

How do you?..... wait...

Textbook way that it should be done, but not as nice looking

It will take the ring out of a panel but a noisy car will still be noisy. For attenuation I like the rubber coated jute type stuff that BMW used to use. My POS 32 year old E28 is orders of magnitude quieter than our Kia Soul.

Enyar wrote: You don't happen to have a roof rack do you?

It does have a rack, but the cross bars are stored on the sides and aren't out in the wind on the 4g outbacks. And for what it's worth the few times I did have my kayak rack up there I couldn't hear a difference.

skierd wrote: Tires are Cooper CS5 Ultra Toruings, about half worn. I don't think it's mostly tire noise, as it's been about the same between these and my blizzaks. I'll probably wear these out by the end of summer, so I'll tackle the tire side then. Recommendations? Drivetrain is stock, and quiet. I actually wouldn't mind a bit more engine noise lol. It's road/wind noise I'm trying to combat. Around town is fine, but over 60mph things get loud, almost a dull roar, in a hurry. I added window visors at the end of last summer which helped with some of the wind noise, but wind is definitely a bit part of it. I usually set my cruise at 75mph and have to really crank the radio to hear over the road.

Tires - go on TireRack and sort by noise level.

Wind noise is generally related to aerodynamics. Bodywork in the air flow causing turbulence and thus noise. At some point prior to my purchase, the driver's door in my van was "tweaked" somehow and there is a bit of a gap at the top-rear corner. That gap is loud as hell, although I've learned to live with it. Or I just drive slower most of the time.

Some years ago, I remember Ford advertising the new (at the time) F-150 having various voids in the body filled with closed cell foam to reduce road noise. Not sure how that could be added later to a vehicle that wasn't designed for it.

I remember the info JKB posted about Dynamat. It's always perplexed me when people cover the insides of their cars with the stuff, but even I (amazing, eh?) have given up on talking about it. I have various ideas about how to improve noise and heat insulation in the classic cars I have, but in those cases I'm starting from a much lower base for improvement.

skierd wrote: It does have a rack, but the cross bars are stored on the sides and aren't out in the wind on the 4g outbacks. And for what it's worth the few times I did have my kayak rack up there I couldn't hear a difference.

That's surprising. My Jetta wagon is loud as hell with the bike rack installed on the roof. Even the wind noise from the base rails without the rack/cross-bars essentially makes the sun-roof an option that never gets used due to how loud the car is with it open. My old Integra and my ex's M3 (cars without roof rails) had sunroofs that were much more quiet when open.

So here's the answer:

Buy a Bolt.

The Leaf was dramatically quieter than any ICE car I have ever been in. I doubt you're going to be able to get a modern car much quieter without a wind tunnel, as I suspect much of it is wind and glass based. EVs end up being much quieter not only because of all of the engine noise is gone, but because the manufacturer has to eliminate tons of noise since the engine isn't drowning things out anymore. The Leaf had a special windshield wiper motor, for instance, and also those goofy mirrors were all for wind noise.

I'd run out of battery about halfway through my out of town days, which are usually 200+ miles and through the hills. I'm also not ready to trust the technology or the range claims at -40 degrees, nor do I think it would get out of my driveway when we get a foot of snow. Otherwise I'd already be in a Volt or Prius for commuting.

Ian F wrote: I'm a bit confused here. This is a 2012 car.

A low end 2012 car built to a price. It's not an Audi, it's a Subaru.

NordicSaab wrote: I just did Noico (see ebay) sound deadening in my 2010 silverado. Did each door with approximately 5 sq. ft. of sound deadening each. The difference is remarkable. At highway speeds the truck interior would have a hum from road noise, now the main noise is wind. Pretty amazing.

Bought the same stuff through Amazon, $63 for 50sqft which is enough to cover the entire floor in my Nova. Plan on doing that along with the aforementioned duct wrap from Home Lowes and that should really quite and cool things down.

Knurled wrote:

Ian F wrote: I'm a bit confused here. This is a 2012 car.

A low end 2012 car built to a price. It's not an Audi, it's a Subaru.

This. Road noise in my 2010 Forte was atrocious on rougher pavement. The doors had zero sound deadening. Rain? HAHAHAHAHA. Not as bad as teh Sierra's roof. Holy hell. When it rains, you can't hear anything. Crew cab roof should have had SOMETHING up there.