Passat Road Noise Measurements

[Salsaman06]

Decided to post this in its own thread rather than hijack someone else's.
Finally got some time to go take some road noise measurements today in my 2013 Passat TDI SEL with the Hankook tires. The weather was overcast but dry and 70 degrees. I took both dBa and dBc measurements. Since road noise lives down in the lower frequencies the dBc measurements are probably more relevant here. The numbers by themselves don't mean much without some frame of reference like the measurements I took inside my house.

Measurement tool: SPL Meter - American Recorder Model SPL-8810 (set to fast sampling mode)

For reference, the measurements recorded from my house below were taken in silence - I was the only person home, the only thing "on" was an iMac about 3 feet away and the fridge about 20 feet away:
33.2 dBa
41.8 dBc
Measurements inside the car were taken at night in my driveway with no outside noise intruding
engine off, complete silence:
33 dBa
42.5 dBc
engine idling, same scenario as above:
46.9 dBa
71.4 dBc


Now the road measurements:
Tire Pressure: 30psi
Mileage on tires: 4300mi
Weather was overcast but dry. 70 degrees outside temp.
On the Road, all measurements taken at 70mph and taken near the driver's head in the interior. Radio was off. Climatronic was off.

1) Road surface = asphalt, condition = average but smooth (prob 5 yrs old)
a) 67-69 dBa
b) 84-86 dBc

2) Road surface = asphalt, Condition= rough - similar to a "pebble aggregate" layer you often find applied on top of a concrete driveway. This was one of the roughest roads in my area that I could find.
a) 79-80 dBa
b) 94-97 dBc with spike to 100 dBc

3) Road Surface = asphalt, Condition = smooth, relative new (about 2 years old)
a) 66-67 dBa
b) 83-85 dBc

4) Road Surface= asphalt, Condition = extremely smooth, very new, probably 6 mo old.
a) 62-64 dBa
b) 80-82 dBc



Tire Pressure: 38psi
Mileage on tires: 4900mi
Weather was clear and dry. 65 degrees outside temp.
On the Road, all measurements taken at 70mph and taken near the driver's head in the interior. Radio was off. Climatronic was off.

1) Road surface = asphalt, condition = average but smooth (prob 5 yrs old)
a) 65-67 dBa
b) 83-86 dBc

2) Road surface = asphalt, Condition= rough - similar to a "pebble aggregate" layer you often find applied on top of a concrete driveway. This was one of the roughest roads in my area that I could find.
a) 75-77 dBa
b) 93-94 dBc

3) Road Surface = asphalt, Condition = smooth, relative new (about 2 years old)
a) 63-64 dBa
b) 83-85 dBc

4) Road Surface= asphalt, Condition = extremely smooth, very new, probably 6 mo old.
a) 63-64 dBa
b) 83-85 dBc

 

[RoadRunnerTR21]

Thanks for taking the time to take the measurements. Do you have access to any other vehicles (VW or other) that can be used as a point of comparison?

 

[tdiatlast]

Great idea. What equipment was used to measure? PSI? Miles on the tires? Ambient temps?
While "YMMV", this might provide a starting point for yet another healthy (OCD!) discussion here.

 

[VeeDubTDI]

What kind of meter did you use for your measurements?

 

[Salsaman06]

Thanks for taking the time to take the measurements. Do you have access to any other vehicles (VW or other) that can be used as a point of comparison?

Yes, I have a Lincoln Town Car which I will do the same test to soon and post here for comparison. I am very curious to see what those measurements will be, given the TC was designed to be quiet and absorb road ugliness.

I also have a Chevy S-10 with a sport suspension. May run that one thru the tests also and post here FWIW.

If I have to drive a loaner vehicle again with VW, I will definitely run that one thru the same tests and post here.

 

[Salsaman06]

Great idea. What equipment was used to measure? PSI? Miles on the tires? Ambient temps?
While "YMMV", this might provide a starting point for yet another healthy (OCD!) discussion here.

What kind of meter did you use for your measurements?

Just added the info to my original post.

 

[tdiatlast]

Thanks for the update. Why such a low tire pressure? Sticker calls for 33psi, many here bump up to 38-40...just curious. I suppose you could be outrageously anal and take measurements at various PSI...I'll wager noise varies a great deal with PSI...

 

[Salsaman06]

Thanks for the update. Why such a low tire pressure? Sticker calls for 33psi, many here bump up to 38-40...just curious. I suppose you could be outrageously anal and take measurements at various PSI...I'll wager noise varies a great deal with PSI...

The car is new. Just bought it in December. The tire pressure is what it was delivered with. I haven't bothered to change it. Tire pressure will surely affect road noise to some degree. By how much is anyone's guess. Maybe after I run the tests on the Town Car I'll redo the Passat with higher pressures. Certainly a test worth doing.

 

[Jbdesigns]

30 psi will be very squishy and fairly comfy ride. I don't run that low and pump up to 42psi all around. Better mpg for sure. I drive a lot and want the extra mpg at expense of a little harsher ride. I wonder about noise diff for psi change.

 

[Herkguy]

Car and Drivers DB tests and my passat results

I found these Car and Driver test results:
Sep 2011
-2012 TDI SEL 17" contis
1. Idle- 47dba
2. Full throttle- 74dba
3. 70mph- 72dba

Aug 2011
-2012 V6 SEL 18" hankooks
1. Idle- 40dba
2. Full throttle- 78dba
3. 70mph- 72dba

Oct 2012
-2012 2.5 SE 17" contis
1. Idle- 39dba
2. Full Throttle- 73dba
3. 70mph- 69dba

Here are my current results after some sound dampening and insulation work.
Car is 2013 TDI SE roof/nav 18" Hankooks w/8400 miles
roads-dry
temp-25F
meter- radio shack
1. Idle- 46dba
2. Full throttle- 64dba <---this was the easiest work
3. 60mph smooth pavement 58dba
4. 70mph medium pavement 60dba
5. 70mph medium concrete 66dba
6. 70mph singing concrete 68-70dba (From previous test)-will update if its better after adding some extra insulation

I'll try and post a few pics of the engine stuff but it basically was just a little GT Mat under the insulator, a little on the top of the firewall behind the insulator and adding an additional gasket seal for the firewall to hood.

I think a lot of the engine noise is transmitted through the upper firewall and windshield.

The rest was adding sound deadner to the doors, wheelwells, C-pillar lower sides next to seats, deck lid and the trunk floors. I then added some sound insulation to all those plus along the lower sill trim panels.

 

[secondtdi]

Seems like a lot of work... I think the greatest contributor to road noise is the composition of the road material. Subjective analysis of course, but worn poor concrete road surfaces sound much worse than fresh blacktop. I think that you must detail the road surface with your test info.

 

[LokiWolf]

30 psi will be very squishy and fairly comfy ride. I don't run that low and pump up to 42psi all around. Better mpg for sure. I drive a lot and want the extra mpg at expense of a little harsher ride. I wonder about noise diff for psi change.

A little MPG at the expense of safety and control...I just don't get it.


Sent from my iPad using Tapatalk HD

 

[tdiatlast]

Loki...that's another thread...

 

[brent_strong]

I'd love some more information on the sound deadening you did, Herkguy!

What products did you use? Approximate cost? Did you do anything to address wind noise? I've slowly started to try to pinpoint mine...

 

[greengeeker]

Does anyone know if the A pillars are filled or is there a noise block between the frame horn and the A pillar?

 

[LokiWolf]

Loki...that's another thread...

10-4, Sorry!


Sent from my iPad using Tapatalk HD

 

[Herkguy]

Brent the materials were fairly cheap.
I bought enough to do both my car and my wifes Jetta so you could cut the cost in half if you just want to do one car.

I used GTMAT sound deadner 80mil as the base layer
-ordered 100sgft for $200.00 on E--Y

as a second layer in the trunk and reaar wheel wells, I used some frost king foam duct insulation from Lo-es home improvment as a cheap decoupler. Its only $18.00 a roll, I used 2 so far. You could find a more appropriate decoupler foam but it will cost ya.

Then i topped it with Ultra touch Radient heat barrier- a foil backed cotton insulation approximatly 1/2" thick from Ho-e Dep-t. I bought the big roll 48"x24' to do both cars. $64 shipped.

I bought a 10' roll of 1/2" or 5/8" car door seal with the self stick 3M tape for the cowl seals from the local auto parts store. $25

so for both cars it cost me $326 in materiels plus any more decoupler foam I may purchase.

Best bang for the buck was dropping the wide open throttle 10db with just a little GTMAT and the door seal material.

I would be happy to go into more detail off line or in another thread. PM your eamil or phone and I can get more specific.

By the way, how do I add photos to this forum? I dont have a web page.

 

[Lightflyer1]

Here using the tdiclub host:

http://forums.tdiclub.com/showthread.php?t=286691&highlight=post+pictures

or photobucket is similar by posting the img link back here.

 

[50pascals]

Are there different sound insulation packages? I have the SEL premium and find it extremely quiet. I've driven many premium brands over the years and this is perhaps the quietest I've ever driven.

 

[PaulB]

Road noise is more important than most people realize.

I have a Freightliner Sprinter which is fairly noisy, even though I have added insulation to it. I once drove from Wyoming to Oregon, about a thousand miles, a trip I had done several times before. By the end of the trip I had permanent tinnitus, which I didn't have when I started.

I don't imagine all the damage was done in that trip or several trips. I foolishly listened to louder than reasonable rock music when I was young, and also had a job at the end of a runway when in the military. But that 24 hours of moderate road noise was the "straw that broke the camel's back".

Take care of your ears on long trips, folks.

 

[Lightflyer1]

or your youth just caught up with you. I blame mine on 4 years as a machine gunner with no ear plugs. Lots and lots of time on the M60.

 

[greengeeker]

Brent the materials were fairly cheap.
I bought enough to do both my car and my wifes Jetta so you could cut the cost in half if you just want to do one car.

I used GTMAT sound deadner 80mil as the base layer
-ordered 100sgft for $200.00 on E--Y

as a second layer in the trunk and reaar wheel wells, I used some frost king foam duct insulation from Lo-es home improvment as a cheap decoupler. Its only $18.00 a roll, I used 2 so far. You could find a more appropriate decoupler foam but it will cost ya.

Then i topped it with Ultra touch Radient heat barrier- a foil backed cotton insulation approximatly 1/2" thick from Ho-e Dep-t. I bought the big roll 48"x24' to do both cars. $64 shipped.

I bought a 10' roll of 1/2" or 5/8" car door seal with the self stick 3M tape for the cowl seals from the local auto parts store. $25

so for both cars it cost me $326 in materiels plus any more decoupler foam I may purchase.

Best bang for the buck was dropping the wide open throttle 10db with just a little GTMAT and the door seal material.

I would be happy to go into more detail off line or in another thread. PM your eamil or phone and I can get more specific.

By the way, how do I add photos to this forum? I dont have a web page.

A true decoupler goes between your mass barrier (GTMAT in your case) and the structure to which it is attached. It makes sense that you noticed the biggest improvement by adding the GTMAT since you improved both the transmission loss of your panel but also reduced the radiation of noise into the interior cavity. Anything you add on top of the mass barrier is mostly serving as absorption of noise within the interior cavity.

I snapped a picture of a sample we have in the lab that has a built in mass layer with a decoupling layer of foam:

 

[50pascals]

@PaulB - I'm a freak for quiet harmonious environments. Even though I regularly like to listen to loud music.

My business had an F-800 with a 5.9 Cummins and it was loud! We lined it with carpet padding - it was dramatically better.

 

[Salsaman06]

Are there different sound insulation packages? I have the SEL premium and find it extremely quiet. I've driven many premium brands over the years and this is perhaps the quietest I've ever driven.

I don't know for sure but I am thinking there has to be. The 2.5 SE loaner I had for a few days was very noticeably less quiet than my SEL.

 

[brent_strong]

Brent the materials were fairly cheap.
I bought enough to do both my car and my wifes Jetta so you could cut the cost in half if you just want to do one car.

I used GTMAT sound deadner 80mil as the base layer
-ordered 100sgft for $200.00 on E--Y

as a second layer in the trunk and reaar wheel wells, I used some frost king foam duct insulation from Lo-es home improvment as a cheap decoupler. Its only $18.00 a roll, I used 2 so far. You could find a more appropriate decoupler foam but it will cost ya.

Then i topped it with Ultra touch Radient heat barrier- a foil backed cotton insulation approximatly 1/2" thick from Ho-e Dep-t. I bought the big roll 48"x24' to do both cars. $64 shipped.

I bought a 10' roll of 1/2" or 5/8" car door seal with the self stick 3M tape for the cowl seals from the local auto parts store. $25

so for both cars it cost me $326 in materiels plus any more decoupler foam I may purchase.

Best bang for the buck was dropping the wide open throttle 10db with just a little GTMAT and the door seal material.

I would be happy to go into more detail off line or in another thread. PM your eamil or phone and I can get more specific.

By the way, how do I add photos to this forum? I dont have a web page.

Thanks so much for the info! I will definitely be in touch when I'm getting ready to do this!

 

[Salsaman06]

Some of you were curious about the low tire pressure (30psi) under which I performed the first measurements and what the difference might be at a higher pressure. Today was another day similar to the day I took the first measurements so I pumped the tires up to 38psi all around and ran the tests again on the exact same road in the exact same locations. The results are added to my original post (#1).

 

[donDavide]

My wife noticed it first, but the tire noise is definatly louder than my B6, I will see when I put my Snowflakes on this spring with either Continentals or Generals. (B6 had Conti) My presures were lowerer than What I normally run, I bumped the up, way up but have not done much driving since.

 

[carlrx7]

Best way to make your car quiet is to own some GM cars! This thing is a dream compared to my Trailblazer SS and C6 Corvette

 

[tdiatlast]

^^^not the best of comparisons...

 

[50harleyrider]

My 2013 SE is quieter than my B5.5s which are much quieter than my previous B4s. What's all the fuss? I can whisper to my wife at 80. Please!