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Reducing Interior Sound - (several pics - long article)
At the request of another forum member (Ralphyboy), I am post pics of my recent sound reduction project with subjective results. This is not complete because the project is still in progress.
I started with the doors by adding Dynamat Extreem to the inside of all the outer body shell surfaces:
Closeup View of speaker hole in Driver's door:
Next I added a layer of Ensolite over the Dynamat - here you can see the Ensolite foam through the speaker hole:
Then Dynamat Extreem was added to the inner surface of all exposed door panels:
Another view showing separate pieces of Dynamat cutout to cover window adjustment holes for future access. It was hard to improve on GMs Rubber/Styrofoam sound deadening insert so it was retained in stock form:
Driver's stock door panel removed:
Ensolite added to inside door panel - last step before reassembling doors:
To do the doors in this manner took me about 10 hours and after this stage I stopped and drove the car for a couple days to see if I could detect an inprovement. While not radical in overall sound reduction it was very obvious that virtually no sound was coming from the doors - and the road noise through the doors was eliminated as much as any luxury car. The way I could tell there was an improvement is that the sound from the rear was even more irritating and directional. So on to the rear...
Here is the first layer of Dynamat Extreme applied to the cargo area showing how I filled all the valleys in the floor molding first. The reason for this is that mass-loading will not have as much effect unless it is in contact with the entire surface it is being applied to so this was my method of eliminating an air pockets by leveling the floor area:
Here is the 2nd Layer of Dynamat applied - view from driver's side:
Another view from passenger's side (Note the air pressure vent flapper was retained and was deemed to be a minor sound leak concern):
View from Cockpit into cargo area (Note: I added two layers of Dynamat to rear wall):
At this point my point&shoot camera died a horrible death and did not want drag out the "big guns" so I will have to verbally describe the next steps for now...
Next step was to add a layer of Ensolite (which BTW I purchased from Rick at RAAM Audio - very helpful and a great product line) to the entire cargo area.
Next I added Dynamat to the vertical separation plate behind the seats. To do all the cargo area and behind the seats took about 12 hours of back-wrenching work.
Next reinstalled all the stock carpet and added the heavy Lloyds Cargo carpeted mat to the cargo area (a very important sound reduction step IMO). At this point I stopped again for a couple days to test the results. Again there was a very noticible improvement, but in my opinion it did more to lower the frequency than eliminate the amplitude.
In preparation for the next phase (which would be the wheel wells), I went to Lowes to purchase some Batt Insulation which I planned to use around the door cracks and gas tank openings once inside the wheel wells (but never did). All they had in stock was a big roll of insulation that filled about half the cargo area on the way home, but this brought something else to light... on the way home from Lowes the car was DEAD SILENT with that roll of insulation in the back and the wheel wells were still exposed to the cockpit, but virtually ALL the tire noise was eliminated (more on this later).
To the wheel wells (sorry no pics yet - P&S camera was still trashed and did not want to drag out the "big" digital cameras around all this car work). I started by removing each wheel well liner one at a time. I added Dynamat to the reverse-side of all four wheel liners and added Dynamat and Ensolite to all wheel-well body panels and exposed frame surfaces. Once inside the rear wheel wells I decided against the Batt Insulation for the door openings, etc. - it just looked like that would end up a breeding ground for mold if it got wet, so I substituted Ensolite instead. Also on the Right Rear there was a large opening in the frame to access the gas tank so I made a special removable Dynamat Plate to seal that area - looked like it could be a pretty good sound leak. After I flanged everything up on the wheel wells it was time for another test drive. Again more improvement - not as dramatic as I had hoped, but definately noticible.
At this point I decided to go back and re-inspect the Batt Insulation in the cargo area phenomenon. If on the way home from Lowes the car was dead quiet with just that roll of Insualtion in the back and the wheel wells were exposed, that meant to me that the bulk of the sound must be coming through the back wall since that is all the insulation roll was blocking to my ears. Of course, there are some other sound properties at play here, but worth investigating. Therefore, I had an unused SleepComfort HighDensity contoured foam pillow in the closet that I decided to sacrifice (what is sleep when you have tire noise) and it fit perfectly against the back wall of the cargo area between the two humps and was the exact height of the cargo rear wall. I took it for a drive and sure enough that killed about 40% of the remaining noise level (and very simple to add). I think I have now narrowed down the way to get rid of the remaining obnoxious noise level, but I will wait until I test my theory to post it. As far as under the seats and console - I will be adding RAMMAT and Ensolite (also from Rick at RAAM Audio) next month to those areas, but I am really not noticing much noise coming from those areas anyway. I am switching from the Dynamat to the RAMMAT because it is much easier to work with - Dynamat not only sticks to everything, but slices up your fingers big time - Rammat was a dream to work with in comparison and generally costs less.
Last Monday I also switched from the GYRFs to the Michelin A/S ZPs. This also really brought the noise level down, but again more in frequency than amplitude. My car now has a very low muffeled tone - all the high-pitched whining has been eliminated. Also after adding the Michelins I immediately started hearing squeeks and rattles in the dash and console panels - so things are really getting quiet. Stereo volume setting is about half what it was previously at 70 MPH for the same listening level. Also for the first time I can now really hear the stock exhaust on acceleration - sounds pretty good now!
I already had my 550 HP 454 in my 1972 Vette with headers and side exhaust when I was 21 and it was great - THEN. Now I am old (56) and need QUIET SPEED! Almost there.
Great write up. I did the Frost king mod with 3 small rolls of Dynomatt Extream two years ago. It did help quite a bit. I also did the underside of the fenderwells and around the gas tank holes. Im very happy with my results but yours must be wisper quiet now. You also spent a fortune on Dynomatt - my 3 rolls were close to $100 and I was only able to use large chunks to deaden the area (worked well). Post more pics when you can.
Just a question - my doors on the '99, when closing, make a "hollow" sound, while on the S/O's '04 the doors seem to sound "better" (of course this is my subjective analysis).
Do the mats assist in making the doors sound more "solid"?
Great write up, I've done similar myself. Also found that gluing ensolite to the backs of the plastic panels on the b pillar helped with this "whispering" noise I was getting in my ear.
Great write up and subjective results. My biggest question to you is this: Any idea on how much weight you just added to the car?
The (3) boxes of Dynamat Extreme (9 large sheets each) I used had a shipping weight of 21# each including the rigid container box so the total useable weight of just the Dynamat was probably about 54-lbs. I also had 3 full sheets left over and at least 3 sheets in waste from odd-sized cut pieces left over. I also installed about half of a Dynamat Door Kit between both doors at about another 2-lbs. Therefore so far I have probably installed about 44-lbs of Dynamat so far. The Ensolite maybe 3-lbs - it is featherlite. For the RAMMAT it is 22-lbs for a 50-foot long roll and I have used about 25 feet of that so far - so add another 11-lbs. That all adds up to a total of about 56-lbs so far. By the time I do under the seats, the console and the pillars using Rammat and Ensolite I am guessing the total will be around maybe 70-lbs.
So about half the weight of a girlfriend and four times quieter.
Must not be too detrimental - I notice Foose uses Dynamat throughout EVERY car they rebuild on Overhaul'n (on the Speed Channel) and most of those are "big" cars compared to a Corvette - a lot more weight added.
Just a question - my doors on the '99, when closing, make a "hollow" sound, while on the S/O's '04 the doors seem to sound "better" (of course this is my subjective analysis).
Do the mats assist in making the doors sound more "solid"?
Yes, it definately made the doors sound more solid (but not Lincoln-Continental solid). I have never worked on a '99 so I am not sure if GM added some additional insulation in later years (I understand they did in the form of the white styrofoam?). The stock insulation in my 2001 doors was pretty good from the factory - I was surprised how effective - but the outer skin really resonates and adding Dynamat to the inside of the outer skin and lower door frame section really helped with elimanating road noise. The Dynamat and Ensolite behind the speakers also improved the sound system slightly. Adding Dynamat to the inside door frame probably had a minimal effect. Adding Ensolite to the curtain door panels was very helpful and also makes for a snugger fit when reattached quenching some squeeks and rattles.
Great write up, I've done similar myself. Also found that gluing ensolite to the backs of the plastic panels on the b pillar helped with this "whispering" noise I was getting in my ear.
Absolutely! I plan to do the pillars at the same time I do under the seats and console.
I have to give credit to Choreo's post about soundproofing, when he said that carrying a roll of fiberglass wall insulation home from the store reduced his car's noise, I got thinking.
I cut 3 pieces of 3 1/2 inch thick fiberglass batt insulations to fit in the rear three compartments. I used paper faced with paper up. 6 inch insulation would fit, but I used what I had on-hand.
The results in cutting noise are AMAZING ! This is probably the best and cheapest mod I have done to my car. Those wells must be acting as "speaker enclosures" and ampliplying (sp?) the sounds.
Z06's who don't even have lids on these wells, do this and put wood or cardboard (carpet covered) over them and you will be amazed.
Yes, it definately made the doors sound more solid (but not Lincoln-Continental solid). I have never worked on a '99 so I am not sure if GM added some additional insulation in later years (I understand they did in the form of the white styrofoam?). The stock insulation in my 2001 doors was pretty good from the factory - I was surprised how effective - but the outer skin really resonates and adding Dynamat to the inside of the outer skin and lower door frame section really helped with elimanating road noise. The Dynamat and Ensolite behind the speakers also improved the sound system slightly. Adding Dynamat to the inside door frame probably had a minimal effect. Adding Ensolite to the curtain door panels was very helpful and also makes for a snugger fit when reattached quenching some squeeks and rattles.
02-23-2007, 04:47 AM
Reducing Interior Sound - (several pics - long article)
