The people who are saying Dynamat is great have not actually tried it on the 996. It's won't really be a fair test since you will be changing the muffler at the same time, but we'll see.

You will quickly realize how well done the stock soundproofing is when you start pulling up the rear carpet. Porsche has also already put soundproofing in the doors. They just put a small piece of Dynamat-type material, but I guess their engineering told them exactly how much and where to put it - because I covered the entire door and it didn't change anything.

 

Exactly. Most modern Euro cars have two things in common, abundance of electronics/computers for everything and sound proofing. You will probably have better results with Japanese cars for example.

Also being an ex acoustical engineer, I can tell you strategic area placement has 90-95% effectiveness vs covering an entire area majority of the time. However the avg joe doesn't know or can calculate these areas and sound deadening companies want to sell as much of their product as possible.

The best thing you can do is to make sure there are no leaks from the outside in. These types of leaks tend to transmit more of the noise.

 

Check out the Sound Meter apps in iPhone/Android stores. you can measure the level of sound in a before and after test and prove one way or the other if the Dynamat works. I used it in a Mini Cooper and measured it and it really helped.

 

Great input all around. I'm going to get an app to measure the sound before I take it in. I'll measure it in a few key places. (Nothing too scientific) and measure it again on the way home. If I have to measure it to notice the difference than I just wasted money. Hopefully the car will be a bit more hushed.

I will leave the modified mufflers on for a week before working on that variable.

I'll be fixing the window alignment and doing deadener at once. So with that, I won't know for sure the singular impact of dynamat aside from it making my car slower

 

Just downloaded Decibel 10th! Seems fun. May not be dead on accurate but at least I can get a measured before and after.

I have a nice set of CDT 3-way speakers which I'm hoping will sound even better after this as well.

 

What are thoughts on doing some form of "treatment" to the wheel wells? In my experience, tire noise is a big culprit inside the cabin area ...

 

If you're talking about the steel wheel tubs, then yes most manufacturers already treat that area by default as that is one of the highly noise prone areas. I've seen it on several cars already.

 

He might be thinking of the wheel well liners (black plastic). I think a true sound blocker might help but a dampener like Dynamat probably won't work. Good news bad news. Shop ran out of Dynamat so I'm rescheduled to next week . Good news is I will have a chance to take some metered sound readings prior.

 

I was thinking more along the lines of "treating" the inner-fenders in some way (undercoating sprays, Lizzard skin, etc.). Has anyone looked into/tried spraying the inner-fenders?

 

Not a bad idea to do inside the fenders.

Ok so I think the app runs a little high overall on the sound measures but I compared my 2007 MDX daily driver with 100k miles on it to my 2002 911 coupe with 30k miles on it. Not because I thought the Porsche should be anywhere near as quiet but just for kicks.

Doors closed, windows up, relatively quiet area
MDX 48 DB
911 58 DB

Engine idling
MDX 58 DB
911 67 DB

At 70MPH the 911 hits 90 DB with the radio off. Seems really high. The MDX is 80 DB. As I approach 80 the 911 gets as high as 96 DB.

At various speeds the gap basically stays the same. +10db.

All of these values seem high. For example a brand new 2014 MDX tested by C&D shows idle DB of 37. The wildcard is the ambient noise and things like that.

At the end of the day I will have some solid measures of the car before and after the Dynamat goes in.

Test conditions: Same roads, typical two lane highway. I ignored readings when hitting bumps (aka, temporary intrusions)

These are all just quick measures from my work commute. Will do something more scientific and controlled before I record my official results.

So far the measures support my observations. The 911 is a loud gal

 

For comparisons, what tires are you running (brand, size, and air pressures) front and rear?

 

I'm running General Exclaim UHPs. 285/30R18, 235/40R18. Tires are nearly new with low mileage. Highly rated by user reviews yet very inexpensive.
Huge noise improvement over the 10 year old Michelin Pilot Sports. The Michelins were probably quiet many years ago before they dried up

36/44 F/R tire pressure.

 

Did some more research and decided to go with 3 different products.

http://knowledge.sonicelectronix.com...mpening-guide/

CLD (vibration reducer) - CONSTRAINED LAYER DAMPER (Dynamat on the metal)

CCF (sound absorber) - CLOSED CELL FOAM (found a low cost one at Home Depot)

MLV (sound barrier) - MASS LOADED VINYL (found a low cost one at Home Depot)

Doors, under the carpets (front and rear), rear shelf, removing the plastic trim panel that houses the rear speakers and will have them do over the wheel wells and behind that panel.

I should have the slowest 996 by the end of this. Going to wire my rearview camera at the same time since so much of the interior will be apart.

 

I recall reading a thread about someone saying that without the centre console in the car there was quite a bit of noise. Might be worth sticking some dynamat under there.

 

There's already factory sound deadening in the key areas of the center tunnel(and most other places for that matter).

I've taken apart my interior and still have my carpet out. Taking out the interior carpet is what makes the biggest difference when it comes to noise IMO.