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.
__________________

What he said.

I've mentioned this before with regards to noise reduction - my Carrera is pretty darn quiet now. I do have a stock muffler and M&K pre-muffler. I also added sound insulation to the floor and additionally to the back shelf.

The three biggest things I found that made a noticeable difference were:

Sound insulation on the floor. I added MLV backed with closed cell foam, just laid down on the floor cut to size.

A new windshield seal.

New, stock engine mounts. Don't buy anything except genuine Porsche mounts.

All these with some MLV added to the back shelf made a nice improvement - much, much quieter than my SC ever was. I didn't rip any of the old stuff out either.

forgot to mention that the factory used asphalt sheeting to "control" noise. it really did nothing other than add mass to the panels. if you decide to apply a cld make sure you remove all the asphalt (i used a heat gun and a 2" scraper).

here is a shot showing the asphalt sheet on my floor

http://i15.photobucket.com/albums/a3...o/100_4606.jpg


here you can see the difference in color with it removed

http://i15.photobucket.com/albums/a3...nterior003.jpg

all asphalt removed

http://i15.photobucket.com/albums/a3...nterior006.jpg

cld applied ( Welcome to Sound Deadener Showdown | Sound Deadener Showdown is what i suggest for materials - don is a great guy)

http://i15.photobucket.com/albums/a3...r/100_5714.jpg
http://i15.photobucket.com/albums/a3...r/100_5721.jpg


since i have a targa and drive about 85% of the time with the top off i did not go for the mlv. seemed kinda pointless when the entire top of the car was open and allowing in everything :)

cabin noise
 

Thanks for your detailed response and the pictures...the only increase in sound in my 87 carrera is coming from my newly installed Monty muffler...
Where should I enhance the sound deadening to deal with it? can MLV go over Dynamat?
can I put MLV on the engine firewall after removing the existing crumbling blanket?
Thanks

in your case i would start by doing the rear firewall and parcel shelf, then moving on to the floor. you really need something between the cld and mlv to act acs a decoupler.

Nice write up nineball! Thanks, that's exactly the kind of info I was hoping to read.

I always find the best way to minimize cabin noise is to leave my wife at home!

If your factory engine sound deadener is crumbling, then yes, you should replace that. It will likely make a small difference. But seriously, if your new muffler is too loud, put the old one back on.

Some of the Acuras use the noise cancelation system, microphones and speakers in the engine bay, some are considering it for exhaust, straight pipes with little sound. The technology has been around for a while, pretty simple, pick up sound waves and produce exactly opposite waves (kinda sorta)

Much, much easier for droning or constant sounds like jet engines, but could be also applied to tire or wind noise.

It'll never work for a wife though...for that you need to make the cabin loud and the ride harsh. ;)

+1000!!! I worked away for days on the rear compartment of my car - down to bare paint, then "quietcar" (3 coats) dynamat, then MLV. The results were fantastic, and I did not have a new gain in weight as the material I removed was at least as heavy as the new stuff I put in, but the single biggest improvement was the change to new, genuine, motor mounts.

I had also previously replaced the foam strip behind the small oblong vents at the top of the rear window with some slightly more substantial foam - which netted some improvement.

In the front, my front trunk hood was not fully closing due to the hood struts being a little too "heavy duty" - I replaced them with normal duty struts and the hood fits better and the resulting seal reduces wind noise from that source as well.

I was previously unable to drive very far without earplugs but am now able to cruise all day without them. Holding a conversation is actually possible!

cabin noise
 

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?

Sounds like you love the exhaust sound, but you don't because it's too loud. Deciding which one will help resolve that issue.

OTOH, you're ready to reduce the dBs and still enjoy the reduced sound. Short of sourcing a slightly quieter muffler, you're left with applying various insulation coatings to the chassis. I'd use a liquid coating and I'd install a new engine pad, but I'd expect only minor sound reduction from just a pad.

Sherwood

the something should be a closed cell foam BTW

be sure the engine side pad on the firewall is replaced

re Sherwood's comment, I can see a set of muffler inserts in your future

You bought a louder muffler, realized it's too loud, and your next course of action is not to install a quieter muffler? Seems a bit silly.

You can be sure that if your exhaust is annoying you, its annoying others.

Easy fix would be to put a baffle in your tail pipe that is easily removed with a quick release pin when you want more flow.

Cabin noise
 

Just to clear the air...I love the sound of my new muffler (monty 1 in 1 out) ....I just want to decrease the volume a little bit...so the advice given in increasing insulation in the cabin fire wall and replacing my engine compartment blanket are very much appreciated.
I ordered the blanket from our host today. I did install "B-QUIET ULTIMATE" last year and based on the various suggestions I will add to it V-COMP which is aready made MLV AND DENSED FOAM.
Any other suggestions are more then welcome

A new engine compartment blanket and plugging the vents at the rear of the roof helped bring the cabin noise in my '87 coupe down to a reasonable. The vents really leave a lot of noise into the cabin.