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Making Golf Interior Quieter

George Ab

Drag Racing Champion
Location
Pacific NW
Completed anti-resonance and sound absorption treatment of my GTI. Noted there is no carpet insulation from the front of the back seat on. No wonder there is so much noise when you put the seats down! The only absorption material was absorption pillow located in the rear quarter panel (still in its plastic, making it useless for the job intended) two 6 X 4x ½” pads on the back of the wheel housing, a patch of carpet insulation on the back of the plastic quarter panels (C pillars). There was fairly good anti resonance treatment, but that is to stop the car from generating noise not kill the road noise from outside. If you have ever pulled a door panel off you will notice that there is both anti resonant treatment and sound absorption curtain attached to panel. Not great sound treatment, but better then most cars.

Typically, to make your car quieter from road noise you start underneath where you sit, but on my GTI from what I am seeing it is from the rear seat back where the thick carpet insulation ends. You have probably noted that most of the road noise is coming from the back of the car. I first did the doors as an audio performance upgrade and went on to the rear of the car to quiet it down.

Weight: Completed the anti-resonance treatment. Supposedly 25% coverage provides 99% performance of reducing panel vibration noise. My technique was if it bongs (large areas that bong when you strike) treat. It is heavy at .7lb per square foot, so another reason to apply as recommended. To treat the rear of the car was about 5 ½ lbs. Now the sound absorption materiel is super light, just over a pound for 19 square feet. 38 square feet covered everything from the rear seat back, so approximately 7.5 lbs of total weight gain.

Costs: I used Noico as it a respectable product and reasonably priced. 36 sq feet of 80 mil dampening material was $64 more than enough for entire car, and $80 in 150 mil sound absorption for the rear of the car which used 36 sq ft. I need another 19 sq ft for doors so total cost is under $200.

The project is labor intensive, it took me a couple of long days. Isopropyl alcohol, wipes, scissors, box cutters, scissors, roller and normal hand tools to remove a few bolts is all that is required along with a willingness for a butt-load of work.
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Is it worth it? My car is no Benz S class quiet, but is quieter than before treatment. Much more aware of wind noise from windows which I never heard due to noise from rear. I did not take any before after dB readings, but I would estimate 3dB reduction at highway speeds. I will be appreciating the noise reduction for some time. I have the “cheap and easy” Fender subwoofer mod http://www.golfmk7.com/forums/showthread.php?t=39460. I noticed improved subwoofer performance immediately, something I was not expecting.[/FONT]
 

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dr_mat

Go Kart Champion
Location
Berkshire
Fresh soft compound tyres will reduce road noise noticeably too, certainly if accompanied with tall sidewalls (smaller wheels).


...if it creaks, it's probably made by VAG
 

George Ab

Drag Racing Champion
Location
Pacific NW
Inspired based on the results of sound treating the rear of the car. Doors are done, inner and outer skins. Going to complete the stereo upgrade next before removing center console and carpet; may do concurrently.
 

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SteveRosenlund

New member
Location
Spring, TX
Inspired based on the results of sound treating the rear of the car. Doors are done, inner and outer skins. Going to complete the stereo upgrade next before removing center console and carpet; may do concurrently.



Please tell me more about the Noico products? I’m really only familiar with Dynamat and Dynapad. How would you compare them?
 

George Ab

Drag Racing Champion
Location
Pacific NW
Noico is highly regarded by installers. Both are butyl rubber with thin sheet of aluminum on outside with stick’em. Dynamat extreme is .44” thick, Noico is .80” thick, both are butyl rubber, Dynamat is $160 for 36 sq ft and Noico is $64. Noico is made in Europe (Russia), Dynamat is a US product.


DYnaliner comes in 1/8”, ¼” and ½” thickness and is one continuous sheet and is acoustic foam with sticky on one side about $44 for 12 square feet. Noico is $40 for 19 square feet and comes in smaller squares so you piece together. These products are used for doors, trunks, etc.



The Dynapad is a different product that is acoustic foam sandwiched between vinyl, I do not believe Noico makes an equivalent product. It is normally used for under carpet in high traffic area and is pretty expensive.
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
MK7 Golf GT Estate
I see many of the threads on various forums & it makes me laugh as the waste of materials....

Those white/yellow pads are good damping pads (VW)....no need to fit damping material over them...

You only need to spot fit damping material (butyl rubber) in the centre of a panel to stop the panel vibrating on its own...much like you place hand on drum to quieten it.....

You then need to sound absorb by placing a thick felt material under all carpets & in small places....

In hollow spaces fit egg crate (cones) shape foam sheet to cancel out any reflective sound waves between parallel metal surfaces...

easy & simple...less material & less cost......done it on previous cars...just our German built ones & UK spec are quite quiet....so I haven't done it on this....

BTW I studied building acoustics design as part of my Uni stuff...& have built speakers etc...
 

southpawboston

Drag Race Newbie
Location
Somerville, MA
I see many of the threads on various forums & it makes me laugh as the waste of materials....

Those white/yellow pads are good damping pads (VW)....no need to fit damping material over them...

You only need to spot fit damping material (butyl rubber) in the centre of a panel to stop the panel vibrating on its own...much like you place hand on drum to quieten it.....

You then need to sound absorb by placing a thick felt material under all carpets & in small places....

In hollow spaces fit egg crate (cones) shape foam sheet to cancel out any reflective sound waves between parallel metal surfaces...

easy & simple...less material & less cost......done it on previous cars...just our German built ones & UK spec are quite quiet....so I haven't done it on this....

BTW I studied building acoustics design as part of my Uni stuff...& have built speakers etc...

Dave, are you saying that the OP used more material than he needed, and that these materials are overkill compared to strategic use of egg-crate foam, felt padding, and a small amount of spot-fit butyl rubber?

Even if there is a diminishing return on investment in the OP's case (in terms of diminishing improvement in sound deadening plotted against expenditure), a total cost of $200 in materials is not really a lot.

Where would you recommend sourcing egg crate foam sheets? I would imagine you can source felt padding from a home carpeting installation shop.

Do felt padding and egg-crate foam sheets conform to fire retardation requirements for automotive use?

Not trying to challenge or play devil's advocate, I'm just in a position of wanting to do this to my GSW this summer and am trying to put a strategy together.

Does the UK-spec MK7 come with more under-carpet insulation than US-spec?
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
MK7 Golf GT Estate
Dave, are you saying that the OP used more material than he needed, and that these materials are overkill compared to strategic use of egg-crate foam, felt padding, and a small amount of spot-fit butyl rubber? yes

Even if there is a diminishing return on investment in the OP's case (in terms of diminishing improvement in sound deadening plotted against expenditure), a total cost of $200 in materials is not really a lot.

Where would you recommend sourcing egg crate foam sheets? I would imagine you can source felt padding from a home carpeting installation shop.

Do felt padding and egg-crate foam sheets conform to fire retardation requirements for automotive use? yes it does if you buy right..I have used auto stuff from kit car builder suppliers..


Does the UK-spec MK7 come with more under-carpet insulation than US-spec? not 100% but we get full german spec on the sound insulation...anyway the aero mods I did have made it quieter...

answers in bold
 

southpawboston

Drag Race Newbie
Location
Somerville, MA
answers in bold

How much have your underbody aero mods cost you in total? From a cost/benefit perspective, I wonder who's gotten the better bang for the buck... you or the OP?

Again, not trying to challenge, just trying to look at your approach and the OP's approach to noise reduction objectively. I've read all your OEM underbody panel DIYs (very will done, by the way!) and considered doing some of them, but the cost/benefit just didn't seem to be there. It would cost me many hundreds of dollars, if not close to $1000, to add all the panels you've added, and the fuel savings and noise reduction just didn't seem to justify the expense. Whereas, the OP has probably made similar improvements to his cabin noise level and only spent $200. He's also thermally insulated his car with the foam panels, so one might argue that he'll make his A/C work more efficiently (if he lives in a hot climate), and therefore his car will get better mileage.
 
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dr_mat

Go Kart Champion
Location
Berkshire
Extra weight makes a big difference to mpg though, not to mention performance. If it's really only 3.5kg added, I'm not sure how much sound it will absorb.
 

southpawboston

Drag Race Newbie
Location
Somerville, MA
Extra weight makes a big difference to mpg though, not to mention performance. If it's really only 3.5kg added, I'm not sure how much sound it will absorb.

Sound absorption material need not weigh much. Resonance deadener is heavy. But it is only used sparingly.
 

George Ab

Drag Racing Champion
Location
Pacific NW
...just our German built ones & UK spec are quite quiet....so I haven't done it on this....

So the German built & UK spec vehicles have felt insulation under carpet from back seat on? Because on NAR insulation stops at the back seat. Adding sound absorption material where there was none has significantly quieted road noise.



It would cost me many hundreds of dollars, if not close to $1000, to add all the panels you've added, and the fuel savings and noise reduction just didn't seem to justify the expense.


My skid plate was $162 (great mod for the engine protection, I did not notice any difference in sound) and all the other panels were $126 so $300 all in (eBay seller for skid plate and e-acca for everything else). I haven’t installed the other panels, so I cannot comment on sound reduction.
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
MK7 Golf GT Estate
How much have your underbody aero mods cost you in total? From a cost/benefit perspective, I wonder who's gotten the better bang for the buck... you or the OP?

Again, not trying to challenge, just trying to look at your approach and the OP's approach to noise reduction objectively. I've read all your OEM underbody panel DIYs (very will done, by the way!) and considered doing some of them, but the cost/benefit just didn't seem to be there. It would cost me many hundreds of dollars, if not close to $1000, to add all the panels you've added, and the fuel savings and noise reduction just didn't seem to justify the expense. Whereas, the OP has probably made similar improvements to his cabin noise level and only spent $200. He's also thermally insulated his car with the foam panels, so one might argue that he'll make his A/C work more efficiently (if he lives in a hot climate), and therefore his car will get better mileage.

So the German built & UK spec vehicles have felt insulation under carpet from back seat on? Because on NAR insulation stops at the back seat. Adding sound absorption material where there was none has significantly quieted road noise.

My skid plate was $162 (great mod for the engine protection, I did not notice any difference in sound) and all the other panels were $126 so $300 all in (eBay seller for skid plate and e-acca for everything else). I haven’t installed the other panels, so I cannot comment on sound reduction.


Firstly I have double checked quickly & there appears to be the same number of items listed for both German & USA cars under sound-deadening...

However tyres & suspension, I have factory sports "Uk" spec, & I am running Michelin tyres which are very quiet for road noise..this is the main reduction.

Next you have to protect the body from getting hit by stones & smooth air flow...so all my under panels & stone guards..& they are peppered with stone chips...but I don't hear much...as they are hitting a quieter material than metal..If you can't fit then use brush/spray on bitumen/rubber underbody coat/sound stonechip protector stuff...also stops metal panels resonating..

In the OP pic of the spare wheel well, he has placed loads of sound deadening black squares...way more than he needs too...you could cut half away & still achieve the same results...as you only need a small amount in a flat section of panel..every crease in metalwork stops resonance & makes the flat sections smaller..

Then instead of the total layer of rubber I would have used a felt material, way better sound qualities as we are adding thickness to quieten the air & outside wind noise, engine noise, tyre noise...not damping the metal body resonance, as the first black squares do this..

Fire retardant felt..usually called black backed felt...great stuff I have used in past, totally cover areas after the spot application of dampening bitumen pads, even underside of engine hood, under carpets, inside doors:-

https://www.woolies-trim.co.uk/product/1384/sound-deadening-felt


Then lastly for hollow spaces between the metal skins of the door use a egg crate foam, stops stand waves/reflective waves of sound bouncing around the flat parallel surfaces ...you could use the felt material as quite good for this also..

As for my car, yes the felt stuff stops at front of rear seat base...no need for under the seat as the seat is the sound insulator & there are already sound/metal panel damper pads there...the spare wheel well, I have loads of tools/cables etc in the first under flor storage space, so that sound deadening as tightly packed....the floor is in high position with another floor covering carpet on top of the VW floor..so that's my sound insulator..
 
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ITGUY

Drag Race Newbie
Location
PA
but would it look cool?? lol How about rubber spray under coating?
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
MK7 Golf GT Estate
but would it look cool?? lol How about rubber spray under coating?

I did mention that product in my above post.....;)
 
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