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Good progress with the sound deadening efforts Yodaone. I once drove a 2010 Nissan pickup that was terribly noisy. I did similar boom mat installation to floors , doors and roof. The road noise in that car compelled me to get it done. I would like to do the same with my 1998 LS400, but its just quiet enough to make me put it off . Do you have any plans for additional layers of closed cell foam and mass loaded vinyl for the floors?
The 1999 LS400 has a fair amount of dampening material on floor pan (but not fully covered so have been filling in gaps) and carpet has a good 3/4" of foam.
I read that the newest Rolls Royce has about 350 pounds of NVH materials.
Am applying NVH materials and posting as I go.
What remains is package tray, trunk pan, roof, hood and trunk lid.
On 1998 -2000.LS400, the rear door access hole cover is made of plastic sheet held in place with butyl adhesive.
Unlike front door panel access cover, the rear has the Door ECU placed there.
Rear door ECU located over plastic cover. DEI barrier material shown with adhesive backing removed save for the area that will cover ECU (to allow future access. Barrier applied over OEM plastic cover. Adhesive release paper prevents sticking to body ECU.
Applying cork to reduce reflected noise in door cavities
Acquired a 36" X 36" X 1/8" "Low-pressure Rubber/Cork Gasket Material Water-Resistant roll of cork from McMaster-Carr, P.N. 9607K83.
I adhesed cork sheeting onto alumium-faced DEI butyl damping material applied to driver's door skin (several years ago) which acts as a secondary decoupling barrier and, moreover, high-performance sound absorber.
Boom Mat or Dynamat damping material is not an efficient sound absorber.
Automotive door cavities are veritable reflecting chamber, so applied 1/8" cork sheeting to about 75% coverage (to match DEI applied area) primarily to absorb noise.
Immediately noticed reduction in reflected noise actuating window motors, door lock solenoids and interior/exterior door latch...
Also felt a noticeable reduction in NVH when closing door..
Discernible reduction in door cavity noise underway
This may also benefit sound quality of door speakers, but have yet to quantify whether improvement here, so will report (and post more images) after treating all four doors.
Excerpts from article discussing benefits of cork as a barrier to sound and absorber of sound:
"Cork is an excellent noise-reducer. It doesn’t take much to get effective soundproofing out of cork. From what I found, 3/32” (just three millimeters) of cork can block up to 10 decibels of sound.
ISound moves in waves. In order for us to hear those sounds, all of the waves need to remain intact. When sound waves are disrupted, sounds are muffled or completely eliminated.
Cork works by breaking down sound waves within the cell walls and diffusing them.
Cork is great for walls as it absorbs about 40% of the sound in the frequency range produced by the human voice. Used on walls or floors cork will deaden vibration and sound transfer by absorbing the noise, not reflecting it like a hard solid surface. Cork will effectively stop echo noise too.
Cork is a great insulator. It ranks second only to felted wool as a thermal insulator, the stuff Mongolian Yurts are made of, and second to solid rubber as an acoustic insulator. It is the cell structure of the cork that gives it its acoustic properties.
Sound Absorption
The honeycomb-like cell structure of cork and the airspaces trapped in the structure make it an effective soundproofing material. A cubic centimeter, approximately 3/8” cubed, contains about 40 million cells. When sound tries to pass through it, it is trapped and absorbed. A thin layer (3/32”) will absorb 10dB of sound.
Noise Reduction
Cork reduces sound and noise vibration by trapping it in its cell structure. It reduces the sound transmission of sound through walls and absorbs the impact of feet through the floor to the ceiling below.
Acoustic Insulation
Cork is used in homes, offices and other buildings to effectively reduce acoustic transmission through walls, floors, and even ceilings. It absorbs the mid to upper frequency ranges and prevents noise transmission and echo.
Cork Noise Reduction Coefficient
The Noise Reduction Coefficient (NRC) measures the average amount of sound an acoustic material may absorb. The scale range is 0 to 1; with 0 meaning no sound was absorbed and 1 that all sound was absorbed. Density and thickness of a material are also factors used when calculating the NRC.
The NRC is usually reported as a percentage. 1-inch thick cork wall tiles have a rating of 0.7, which means 70% of the noise is absorbed and 30% is reflected.
The Sound Transmission Class (STC) is used in the US to rate ceilings, doors, interior and exterior walls, and windows for sound reduction. The ISO (International Organization for Standardization) is similar to the STC, but used outside the US."
I'm interested in all of this. Please keep it coming. I want to eventually get to improving sound deadening on mine once I get the important mechanical maintenance out of the way
09-12-18, 08:28 AM
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