2nd Gen Non-Engine/Transmission Noise reduction effort update

[Pit Bull]

This works for my wife to quiet my snoring, buy some ear plugs.

 

[GLASMITHS]

Snoring?

PitBull: a cold foot in the back is the best way. Kinda dangerous, but... ... ... .....



moparguy: I have a 30 mile trip for tomorrow, will take the meter with me. However, I WILL NOT put my auto in N at 60mph! I will shut the controller off so the t/c will unlock, that will be the same thing.



What surprised me was the exhaust. My driveway is concrete, in 10X20 ft sections, and the section that the rear of the truck was on had a harmonic vibration that made your feet tingle





george

 

[GLASMITHS]

A couple of observations

On my little trip today (9hrs labor there)- The noise level was the same on passenger side at 55 mph. From the driver side at chest level, then the wife held it on her side and it was the same, 78db. It was different at idle (lower). Ofcourse that would be the exhaust.



With the truck coasting at 55mph unlocked, it is 9db quiter.



Also, one area that has been overlooked in this thread; the engine seal at rear of hood; and also the hood itself. Put the meter about half way down the dash towards the windshield and you get 87db . That seal is crap. I had already worked on mine, but not for sound; so the engine fumes don't get into the vent. I like to run with a/c off and vent when it is cool and not humid; AND after eating at Cracker Barrel .



Greg said earlier in THE post that he had put a strip of foam in his, and I believe there was some pics. This sounds goods, there is a lot of noise comes in through the windshield. Also the doors. If you put the meter up close to the doors it is 1-2 db higher than in the center of the cab.



later



george

 

[GGibson]

Theory of why lead works?

I can understand how adding mass to flat panels can reduce the resonance and therefore sound transmission. My guess is that the smaller radius curves in the panels would not tend to resonanate nearly so much because they would be "stiffer". My question is this. . Would I get basically the same affect by adding lead to only the flat panels and not worry so much about trying to neatly cover all the smaller curves?



Another approach might be, flat sheets of lead on flat panels and then just a lot of 2" squares applied to the curved areas. Seems like you might get the same affect without all the work of trimming in the corners for complete coverage.



What do some of you technical guys think???



Seems like a lot 2" squares on the door panels might be effective, especially where it's so cluttered with stuff and hard to install a full sheet.

 

[moparguy]

9db quieter is a lot. I spent 2 days, 2 1/2 years ago on my truck and was considering doing additional work since you guys have been making so much progress.



I'm seeing 85db at a constant 60mph cruise holding the meter over the console at ear level. Coasting at 60, saw 83db. I'm not sure it's worth a lot of work on the engine since I'd only be chasing a couple of dB's.



One thought about comparing readings from different dB meters is the fact that they likely are not all in calibration, mine could be reading high, making it good for my application, but may not be good for comparison with others.



I also suspect my straight through muffler and 4. 1s don't help any.

 

[Lsfarm]

Noise Leveles and Lead

Hi GGibson, I think you have the idea of the lead sheet exactly right: Adding the lead sheet to large flat panels will add mass to the panel and change it's resonance frequency. . It will take much more sound pressure to start the heavier panel to vibrate and transfer sound. And the heavier panel will vibrate at a much lower frequency.



The short radius compound curved areas are much stiffer and won't vibrate very easy to start with. But adding a piece of lead to the smaller curved areas still seems to 'deaden' it's noise transmission abilities. An unleaded metal will make a sound like 'tink' when tapped with a screwdriver, but will only 'thunk' once it is coated with a lead layer.



When I coated my oil pan with lead, I got a 2Db drop [average] from a single layer of lead. It does work!



I'm not sure about the added value of making a virtually seamless unbroken layer of lead on the floor and back wall, but it sure looks nice when done I'm pretty sure that a patchwork of smaller pieces of lead will work just as well as one large sheet.



Think about an inexpensive hollow core door in a house, and thiink how well it lets sound through, then think about a heavy solid core door, and how it seems to block so much more sound. The same prinicples apply with our truck cabs.



Moparguy: using the same test parameters, 60mph, meter held at ear level, I see 77-79Db depending on if the meter is aimed fore or aft. A 3Db drop is cutting the noise levels in half, this is a huge difference. I see 83Db at 80-85 mph.



To 'test' your meter, set your fan on high, dash vents open, you should see about 78Db with the meter on the center armrest. Using the C scale on your meter [standard readings] This is with the engine not running.



If you try a few of the noise reduction methods and products discussed here, I'm sure you will appreciate the lower sound levels at cruise.



George: I think a lot of sound comes through the metal panel that is at the base of our windshield. This is the metal 'cave' or 'cavern' that is part of the cowl structure and provides the air intake passageway for the HVAC system. I need to duplicate your test, to see if it is any different with all the foam etc that I have applied inside this 'intake area'.



The added foam seal behind the factory 'tube seal' at the back of the hood was quite effective, I also added a foam seal at the front of the doors, ahead of the factory seal. Both made a big difference.



Take care all !



Greg L The Noise Nazi

 

[Partyat33]

I am now on the noise warpath. Been reading this and the initial noise reduction thread. It the best place to star on the back panel ?



My local plumbing supply has 3' X 3' sheets of 2. 5 lb lead for $ 25. 00. Will that work ? Or is it too thick ?



Thanks



Dennis



Noise Nazi in training !

 

[TomGolden]

I would say the rear wall inside the cab is a fantastic first place to start. You can do it without having to pull the front seats and the carpeting all the way out.



Not sure about the lead, as I have so far only used the GSI foam.



Tom

 

[GLASMITHS]

Ditto on the back wall

From my db meter, there is more noise coming in from the back wall than engine, at 55 mph. Also, you are going to glue it in? 2. 5 is a little heavy, but it wont't hurt anything, except for weight.



geo

 

[cmckinney]

I never noticed a difference with the back wall covered. I put some Brown bread (dynamat knock off) on my floors and back wall but I still have alot of sound in my cab.



The biggest difference I've seen is putting a hood insulator in the engine compartment. On the 2002's you didn't get that luxury. I think I'm going to stick with targeting the engine compartment and the floor.



-CM

 

[GLASMITHS]

Hood Insulation

CM: It appears to me (from the db meter) that there is a lot of noise comes in through the windshield; and ofcourse insulating the hood will help this. Also put a 1' foam gasket at rear of hood. The factory rubber gasket is there to keep the engine compartment fumes from the fresh air intake vents.



IMHO, if you do not glue the insulating material down the benefit is going to be marginal. It needs to become part of the metal.

 

[KL]

Dennis, I agree with Tom that the back wall would be a great place to start. I put sound deadener on the back wall first and put the GSI Sound foam over that. I think using both would provide excellent results. Let us know how the heavier (2. 5 lb) lead works out. Klaus



I think I need to buy a Db meter, anyone know where you can get a reasonably priced one?

 

[KL]

GLASMITHS, did you use GSI Sound stop foam or regular foam to make that 1" foam gasket you mentioned for the rear of the hood? Thanks Klaus

 

[moparguy]

KL, I bought my meter at Radio Shack about 6 years ago, don't recall the price, but it wasn't much.



RJR

 

[GLASMITHS]

foam Gasket

KL - I would assume that any foam would do, however, I would personally use 2 layers of soundstop or GSI what ever. I have not done it as yet. Greg did and there is a pic on the other thread.



On the db meter, mine came from action-electronics.com, $97. 29 total. Kinds econ type, but works.

 

[Lsfarm]

Lead, foam and meters

Partyat33: that lead sounds perfect, not a bad price either. The lead I used was 2# per sq ft, so yours is only a bit heavier, and that is to your advantage.



KL: I think that two layers of GSI form glued together would make an effective foam strip for the hood gasket/seal. I had a piece of a different type of foam that I used for this location.



The meter I bought came from Radio Shack, a digital Db meter. Cost was around $50.



Take care, Greg L. the Noise Nazi

 

[kchristopher]

How well do you guys think using rubberized undercoating would work? I've done a few searches and saw the idea mentioned, but not much on results or opinions. Seeing as how you can get this stuff in a spray can, application would be really easy, especially on the back wall. A good thick coat of rubber should add mass and reduce vibrations, wouldn't it?



Opinions?



I thought about using roll-on roofing asphalt material glued down with roofing tar on the floor. Inexpensive and abundantly available.



Opinions on this?

 

[GGibson]

Wiper Blade Assy. Removal?

I want to remove the wiper blade assy from the splined shaft that it is attached to. This is to get access to the areas of air intake so I can apply some foam. How do you get this assy off without destroying the blade assy? Is it just lightly pressed on the shaft or is there some sort of set screw I can't see?

 

[Lsfarm]

wiper blade/arm

Hi GGibson, look at the wiperarm at the hinge joint next to the splined end of the shaft. You will see a little tab sticking out from under the arm. Lift the wiper/arm up off the windshield, and using a fingernail or a small screwdriver pull the tab out to the side of the arm



This tab is a spring tension block. once the tab is pulled out, and you let go of the wiper/arm, it should be holding the wiper about 4-6" off the windshield.



Push the arm towards windshield, and this will un-jamb the arm from the splines, and the arm will lift straight off the splines.



A lot of expaination for a simple task, but once you do it it will make sense.



The only thing keeping the arm on the pivot is the jambing of the splines from the one-sided spring tension of the arm.



Hope this helps, Greg L The Noise Nazi

 

[cmckinney]

GLASMITHS



Do you have any pictures of your insulation in the hood area? I'd like to see something so I can get a good idea of what to do.



Does anyone know where you can get the GSI foam without ordering it?



-CM