The website: http://www.sounddeadenershowdown.com/

The writer didn't cover the liquid coating materials. However, the test results makes choosing mat-type insulation less confusing.

Sherwood

Interesting. Where did you read that? If you go to the quietcar.net they specifically state the product should be applied to metal surfaces. Perhaps "over" was used in place of "versus"?

Thx for that detailed post, Jon. Yo didn't happen to weigh the gallon did you?

Assuming a gallon of paint is mot much more than a gallon of water (8 lbs.); x your 25% guestimate; /2 for the amt. used.... gives maybe 4-5 lbs. of liquid. The wt. will be less than that guesstimate as the liquid fraction evaporates.

So, we might have 3,4,5 lbs. that you think is "at least as effective" in noise reduction as the 30 or so lbs. of stock padding...

Also, did you get any sense of a resonant frequency? i.e. louder at a certain rpm?

Unfortunately, I'm one of the 0.001% of the population that does not own a bathroom scale so I don't have exact numbers (or any numbers for that matter). Regarding resonant frequency, I would say that the paint does a better job than the factory insulation. At about 5k rpms things used to get really raucous in my car (aurally speaking), but my sense is that things have improved. Overall, the interior is quieter throughout the rpm range and under varying levels of throttle (less resonance). One other thing that I should mention is that my road tests were conducted with both windows down (it was pretty toasty outside yesterday), but I drove to and from LA with both windows down as well. I'll get out today for a drive with the windows up.

Rusnak... a change in sound level of 3 db or 3 decibels is typically what is required for a human to detect that there has been a change in volume. The golden ears folks will say they can hear 1.5 db changes.
I found a sound spec for a boxster S ..50 db at idle and 70db at 120km/h. Now normal conversation about 60 dB and a lawnmower is around 90 dB. Any sound above 85 dB can cause hearing loss, and the loss is related both to the power of the sound as well as the length of exposure. You know that you are listening to an 85 dB sound if you have to raise your voice to be heard by somebody else...typically what I do in my targa when I'm talking to my wife.
I'm going to keep searching I recall seeing interior noise level specs for 911's somewhere.

2007 GT3
INTERIOR NOISE
Idle (dBA): 57
Full throttle (dBA): 92
Steady 60 mph (dBA): 72

Jon -

That QuietCar sounds outstanding. You say the brush-application method is ugly; any chance of a pic? I'm thinking that eventually I would want to apply a sound absorbent material to all the areas that show grey in emptyo's pic. For now, however, gutting the interior of my car is not something I find appealing until a resto is in order (it's 30 years old and looks great - would probably cause too much damage trying to pull/replace it). In the interim, the floors could be a good candidate, so that pic would be really helpful.

Also, I've been mentally debating the benefits - or lack of - in applying this to the door panels on the inside, then something like dynamat to replace the plastic sheet behind the upholstery. Since you have experience with the QuietCar, what's your opinion of this?

If the headliner ever comes out, the roof will definitely get a coating of this stuff.

Many thanks for posting your results.

Jim

No pics, but if you're going to put carpet down over it then it's not really an issue. What makes it ugly is the fact that you can see brush strokes, so it's not a nice even appearance like you would get if you sprayed on the paint. It does self-level to a certain extent. You could also sand the paint smooth after it hardens and then apply a top coat of paint. The only time that I remove my floor carpet is to thoroughly clean the interior or for a track day, so personally I wouldn't hesitate applying the stuff on the floors.

The plastic sheet behind the door panels is a moisture barrier and is what keeps water from warping the panels. When the car gets wet, water can (and does) get in the doors. If I were you I would remove the panels and the sheeting (carefully) and apply the paint to the inside of the doors. I plan to do this too.

Great! Looks like I can just brush it on top of the rubbery coating already on the floor.

I know about the water path within the doors so I'm planning a couple of days in there to find and kill any rust that might be forming. Definitely will do the QuietCar treatment in the doors when they get to the top of the do-list.

While I was thinking about all of this I recalled that the last time we took the 911 camping I put the sleeping bags in the back seat - the car was noticeably quieter, so that would likely be a prime location to apply a sound absorbent coating for anyone who can get under the upholstery.

Thanks again, Jon.

Ron,

Thanks for the explanation re: sound levels. I think +/- two or three decibels is ok for our use. I'll see if I can get one at Radio Shack and let you know how loud my 911 is.

I'm hoping to suffer some hearing loss, because I am one of those people who get headaches from burglar alarms at banks, computer hard drives, and I can hear most older style garage door openers.

I don't think most of the sound comes through the floor to be honest, you guys. I think most of the sound comes from the engine through the firewall and center tunnel, and from the tires through the wheel wells. Thats were I would focus my sound deadenting materials. Also, as I mentioned you need a sweetly adjusted door and window frame to cut down on wind noise from the mirrors and rain drip rails.

Ok, info from Paul Frere's Porsche 911 story. A 1979 SC at 100 kph [62 mph] has a noise level of 73 dbA and at 140kph [86 mph] a noise level of 79 dbA. Mister Frere states that the lower noise levels [as compared to earlier models [2.4 911S 76 dbA and 81 dbA respectively] had to due with improved sound deadening and higher gearing. I would bet the readings are a bit optimistic and taken on a good day in a car with a cloth interior.

sound might come from the floor on a wet road or a bumpy one if the bumps are a certain size

when I was a kid, my dad had a 911E with the oil filler on the rear fender [Edit: the 911E I'm told was a '72, thanks, jac]. He sold it when someone sideswiped it, then got a '78 SC. He complained that he could barely hear the motor. He still has that SC, but rarely ever drives it. I use it as a time capsule reference car on my 3.2. Comparing back to back, the time capsule car is quieter. I have no reference to 79-81 db. Once I know, I'd have it locked in and I'll know if my car is lower or higher than that.

At least we're moving toward quantifying our numbers.

Factory right rear fender oil filler door only on the 1972.

The early cars are definitely louder. A friend bought a 71T in Colorado and drove it home to Oklahoma, around 750 miles. His ears were ringing when he arrived.

Now, on long trips the radio sees less use than earplugs...

JR

The early cars are definitely louder. A friend bought a 71T in Colorado and drove it home to Oklahoma, around 750 miles. His ears were ringing when he arrived.

Now, on long trips the radio sees less use than earplugs...

JR

Thanks for the dB post Ron. Let's back up a bit and make sure we all have the basics down. I edited some of my lecture notes on vertebrate sensory systems to give an overview of what we are talking about here:

What is Sound?

Sound is just pressure waves of compression and rarefaction in an elastic medium; can travel in gas, liquid, or solid.

Speed in dry air at sea level = 330 m/s (travels faster in liquids or solids).

2 Properties of Sound contain everything about a sound wave:

Frequency (Hz) -- number of waves per second (or wavelength)

Amplitude (W or db, decibels) -- size of each wave

Humans hear from about 20 Hz to 20 kHz (children) or up to 16 kHz (adults); below 20 Hz is subsonic (rumble); above is supersonic


I don’t want this to get too physiological, but for the engineers out there, I will mention that a structure called the basilar membrane can do a Fourrier transform right there in the inner ear.

Auditory Threshold (softest sound) -- 10-17 Watt, right at noise level of ear

If ear were more sensitive, would hear air molecules crashing into the ear drums all the time ---> selection has pushed evolution to the physical limit.

the ear has a huge Dynamic Range ~~ 120 dB

Can Resolve changes of 0.1 to 0.5 dB, depending on type of signal

The human ear is most sensitive to sounds in what we call the mid-range, and less sensitive to higher and lower frequencies. There are two weighting scales in common use for measuring sound intensity – the A scale and the C scale. We only need to worry about the A scale. for more info Google on these terms and the names Munson & Fletcher.

dBA (note the proper caps are shown here, though often dbA is used) is the most commonly used unit of sound intensity (aka, sound pressure level, aka SPL). It means we are measuring in “deci” (or tenths in SI units) of a Bell (the real or base SI unit for SPL) and using the A scale.

So, xx dbA means xx deci-Bells of an amount or intensity of sound, and it is weighted for the sensitivity of the human ear.

Actually, this involves the logarithmic ratio of different numbers, but I am gonna KIS. We need to compress the measurement scale (which is what you do when take the log of something) because of the huge dynamic range of the ear noted above. What this means for us, is that a dB scale is all relative. We usually set it as relative to the faintest sound that a model human can detect - not your Grandpa who used to crawl inside the speakers at rock concerts and then got struck by lightening by operating a jack-hammer - a young human with 'perfect' hearing.

Now, here is a relative table of familiar sounds. Note: these are NOT adjusted for "annoyance value" - some sounds or patterns of sounds are more annoying than others, even at the same SPL (examples might include a baby crying, a teenager whining, your wife asking for a home repair for the 11th time, chalk scratching across a blackboard, etc.)

http://forums.pelicanparts.com/uploa...1216149280.gif

Here is the info Ron posted in table form; compare this with the familiar noises table above.


http://forums.pelicanparts.com/uploa...1216149590.gif

BTW -
[1] hearing loss can occur at sustained SPLs as low as the 85 or so.
[2] There is no way to repair hearing loss.
[3] Hearing loss occurs BEFORE you feel pain from the noise.
[4] Louder mufflers sometimes make LESS hp on a motor than quieter ones.

Just a safety message... We had a kid die here yesterday in one of the rivers. This was just after I cautioned another kid (these were both college student "kids") about her tubing trip down the exact same spot in the river. The guy that died was a top athlete & football player and apparently very nice guy and level headed. He did not appear to hit his head, but the river caught him anyway.

So be careful and be careful with your loud noises. If you are setting off car alarms you are surely damaging your own hearing.