How to minimize Cabin noise

[Jonny042]

Originally Posted by david.avrahami@

Johnny042, what do you mean by the rear compartment of the car? are you referring to the engine compartment fire wall? or the back seats area?

Sorry, yes, the interior of the rear of the car. The entire rear shelf area, rear seat area, etc.

I did also do an engine compartment sound blanket (lightweight style) but honestly thing the heavyweight style would block more noise.

[Ttownthomas]

Originally Posted by nineball

to really "block" noise it is a 3 step solution.

1. apply a cld (constrained layer damper). this is what dynamat xtreme and second skin damplifier / damplifier pro is: a butyl-based rubber with a layer of adhesive on one side and a layer of aluminum on the other. the adhesive side is applied directly to the metal panel, the butyl converts vibrations into low level heat which is then dissipated by the aluminum. you only need 25-40% coverage on large flat panels for this to be 100% effective. there is no need to do 100% coverage as you are just wasting time, effort and product (money).

2. apply a ccf (closed-cell foam) decoupler. most people use ensolite, or a similar closed-cell foam product. thickness varies but a minimum is 1/8", up to 1/4" will work as well. this acts as a separator between the cld and mlv and also serves to block some of the spectrum of sound. some come with adhesive applied already but if not something like 3m super90 spray adhesive will do the trick. this needs 100% coverage.

3. the last step, and the one that actually blocks (or repels) the sound is mlv or mass loaded vinyl. the optimal solution for most car applications should weight approx. 1lb/foot, and this needs 100% coverage to be effective. you also need to seal up any seams as noise (like water) will find the path of least resistance. overlapping the mlv and sealing it with a contact cement-type glue is the best method but you can also use a heavy duty tape.

if you have any questions feel free to ask.

ps> applying steps 1 and 2 to the inside of the outer skin and inside of the inner skin of the doors will greatly improve your audio output as well. the cld helps with vibrations caused by the speaker and the ccf absorbs the backwaves of the speaker.
__________________

Nineball,

Can you give us more detail on the ensolite specs and any other brands we should try. I looked up ensolite and what I found looks really thick. Also what brands/specs of mlv do you suggest.

[RWebb]

post your location, as the shipping charges for mlv may dictate where you buy it

[Ttownthomas]

Originally Posted by RWebb

post your location, as the shipping charges for mlv may dictate where you buy it

Raleigh nc

After further research I would prefer a ccf + mlv composite.

[nineball]

Originally Posted by Ttownthomas

Raleigh nc

After further research I would prefer a ccf + mlv composite.

install is easier if you do them on their own.

Hang or Secure Barrier Layers (MLV/CCF) | Sound Deadener Showdown

[Ttownthomas]

Originally Posted by nineball

install is easier if you do them on their own.

Hang or Secure Barrier Layers (MLV/CCF) | Sound Deadener Showdown

Just read this link. Thank you. I am specifically interested in the parcel shelf area as it is apart due to an audio upgrade I'm working on.

I have read all your posts and I think I need 25-40% coverage with a butyl/foil dampner and then ccf 100% and mlv 100%. Are you suggesting with the above link that I don't need to "glue" the ccf to the shelf if I glue it to the mlv? Why not just cut it to match the factory pad and reinstall it with the sheet metal tabs?

Why would that be better or easier than a b-quiet type material that is ccf and mlv in one?

[nineball]

no, you don't need to glue the ccf or mls. using don's velcro system you don't permanently adhere either to the car. they are just as effective as a floating barrier. the cld does need to go directly on to the metal to be effective.

when installing you want the seams of the mlv to overlap. when the mlv and ccf are one piece that creates an even thicker seam if you will, 1/8" thicker on every seam, thus harder to seal.

[RWebb]

IIRC, the Showdown guy is back East somewhere...

[Ttownthomas]

Originally Posted by nineball

no, you don't need to glue the ccf or mls. using don's velcro system you don't permanently adhere either to the car. they are just as effective as a floating barrier. the cld does need to go directly on to the metal to be effective.

when installing you want the seams of the mlv to overlap. when the mlv and ccf are one piece that creates an even thicker seam if you will, 1/8" thicker on every seam, thus harder to seal.

Ohh... I see. So can the ccf pieces simply butt up to eachother and you cover the seams with mlv?

[nineball]

Originally Posted by Ttownthomas

Ohh... I see. So can the ccf pieces simply butt up to eachother and you cover the seams with mlv?

yep. the ccf is just a decoupler, the mlv is what blocks noise.

[Ttownthomas]

Originally Posted by nineball

yep. the ccf is just a decoupler, the mlv is what blocks noise.

2 more questions

1. Will ccf and mlv fit between a 911 door card and the inner skin?

2. Why, on your audio install, did you do 100% dampner coverage on the doors if 25% will work. On Welcome to Sound Deadener Showdown | Sound Deadener Showdown this is said to be unneeded?

[nineball]

1. probably not. most installs apply the ccf and the mlv to the inside of the outer door skin.

2. for audio reasons. it's called "sealing the door" but no door will ever really be sealed, you will always have the drain holes in the bottom. by covering the holes in the inner skin you form more of a chamber for the door speaker, which improves output especially on the lower end of the spectrum. it's no substitute for having a sub but it will increase your low output.

[Ttownthomas]

Originally Posted by nineball

1. probably not. most installs apply the ccf and the mlv to the inside of the outer door skin.

2. for audio reasons. it's called "sealing the door" but no door will ever really be sealed, you will always have the drain holes in the bottom. by covering the holes in the inner skin you form more of a chamber for the door speaker, which improves output especially on the lower end of the spectrum. it's no substitute for having a sub but it will increase your low output.

Did you put mlv in your doors?

[nineball]

nope. i have a targa and ~85% of the time if i am in it the top is off. no amount of any product can overcome the roof missing my approach was audio-based not trying to eliminate exterior noise. my daily driver did get the full treatment though.

[RWebb]

for the parts of the door closest to the occupants, use the heat shrink/moldable stuff by CAE

Automotive Noise Control - Soundproofing

don't forget to dampen the door skin

it will add wt. to your car

[nineball]

Originally Posted by RWebb

for the parts of the door closest to the occupants, use the heat shrink/moldable stuff by CAE

Automotive Noise Control - Soundproofing

don't forget to dampen the door skin

it will add wt. to your car

the cld and ccf add barely anything, and in fact there was a weight savings after removing the factory asphalt sheeting and rear pad. the mlv is where the weight comes in as they are typically 1lb/sqft.

[88911coupe]

Nineball offers a lot of good advice here, along with others as well. Something I've never really understood is does the sound come THROUGH the body or is it being reproduced by the car body...or both? If it's both (as I suspect) which one are we most interested in stopping or at least mitigating? I enjoy the engine noise much better when the windows are down that the noise I hear coming from the back with the windows up. I'd also like to get rid of the "tinniness" of the noise. Looks like I'll be using some of Nineballs good advice and tricks.

[david.avrahami@]

Why do we need CCF in the 3 step process? I already have # 1 with a foil exposed on top....can I not just put the MLV to cover it?

[RWebb]

it's both - but dampening the car body will [1] attenuate the sound from the vibrating panel, and [2] shift the frequency of the vibration to a lower freq.

the closed-cell foam isolates the MLV from the vibrating panel & dampener

[david.avrahami@]

Thank you all for the advice....job done! results are good .../\still have a great sounding 911...but not as loud.
I still have to replace the engine compartment blanket...but worried about removing the air filter box and meter as well as the heater fan to make some working space...