Note that the weight data given apply to materials whose sole purpose is to reduce sound penetration into the passenger compartment. Carpets, roof lining and seat upholstery also reduce sound levels but are not usually considered part of the materials tally for soundproofing.

Reducing vehicle weight by 8kg isn't going to make a significant dent in fuel economy, but as always, something is better than nothing. For manufacturers, the real upside is reduced cost (less soundproofing mass is equally effective) or increased luxury (same soundproofing mass is more effective). Chances are, most will decide to increase luxury because that boosts margins significantly whereas improved fuel economy doesn't.

The auto industry should look backwards and take a lesson from history and try to figure out how Sir Alec Issigonis and his huge engineering staff of 6 people managed to produce the Mini in 1959. Without any lightweight modern materials and a cast iron engine/tranny the 4 passenger Mini's weight was only 1357 lbs.
http://en.wikipedia.org/wiki/Mini

So, would you rather drive/ride in a '59 Mini, or its modern incarnation?

Cervus--

What kind of response from the prior poster are you expeting with that kind of question?

Steve:

Mainly, that the regulatory and consumer preference environments are much different now. Safety regulations and emissions equipment adds a not-insignificant amount of weight to vehicles that size. A modern mini weighs 2600 pounds and still gets 40mpg highway with a stick shift.

You won't find many cars that weigh less than that.

How about active noise cancellation system? Most cars already have a multi-speaker sound system. Adding some circuitry and a set of microphones to create a far more effective active noise cancellation system would add negligible weight, but far more effective at sound damping.

Reducing noise in the interior is not always a question of sound insulation. Tyre noise can be reduced significantly by a special tread design. The road surface is also a important factor. It seems that mixing the asphalt with rubber (recycled car tyres) also has a positive effect on tyre noise.

There is another advantage to this approach. It is not only the occupants of the car that enjoy the noise reduction, but also the people living near busy roads.

Perhaps something which would help to reduce road noise would be plastic wheels. Plastic wheels would also contribute to reduce the weight of the vehicle.

Roger,

Take a ride in a car with a multi-channel audio analyzer + multi-channel DAQ for about a week and you start to see that the amount of DSP horsepower (not to mention significant programming) is far from trivial. Isolating one frequency that is not time varying nor changing in harmonics, intonation, amplitude, or frequency may be child's play but even the different occupants in the vehicle will have an impact on the sound transmission. I would guess that you are suggesting the auto-makers spend $1000 per vehicle for sound deadening that can be done by $2-3 worth of material.

[some vehicles do use active noise cancellation but I believe it is limited in frequency to only the most common & harshest frequencies]

Heck, even a david-clark or BOSE headset for aircraft (which have a much more constant noise pattern than a car) run over $1000 and they have the advantage of the ear muffs providing a great amount of attenuation on top of the active noise cancellation.

Actually I would rather be driving an updated version of the original Mini than that over-sized bloated thing BMW calls a Mini.

Just replace the old fashioned cast iron BMC 'A' engine/tranny with a new 1.0 L all aluminum BMW designed engine/tranny. Add all necessary the smog & crash additions and you would still have a simple unbloated 4 passenger car that weighs between 1500-1600 lbs with 100HP getting mileage in the 55mpg range that is fun to drive.

Patrick,
Anything involved with aircraft is produced in very limited quantity and tend to be ten times more expensive than mass-produced automotive components. I believe that non-aviation noise-cancelling headsets are sold for much less than $1000, may be about ~$100.

Honda is now using noise-cancellation technology in their Japan-only Accord station wagon.
The way it works is that a microphone connected to the car stereo system picks up all the sound inside the car, including music or such from the stereo. Then the noise-cancellation system subtracts the sound of the music coming from the stereo and produces noise-canceling sound waves that match the frequency of unwanted sound.
The noise-canceling sound waves are also sent through the stereo speakers, along with the music. This technique greatly reduces the low frequency vibration noises in the car, without dampening the car's audio system.

DSP chips are getting much more powerful and cheaper than ever, and with lower power consumption as well. Development cost (programming) spread over millions of copies yearly will be small for each car. Of course,the number of sound frequencies to be cancelled will be dependent on the processing power of the DSP chips on board. Road noise and engine noise tend to be of lower frequencies, and hence required less processing power than human speech, which you do not want to be cancelled out ( except when kids are crying or yelling inside the car!)

The article states: "Applying the project results to a simulated car—a Renault—resulted in an overall weight reduction of 6.7%. Applied to a real Citroën C4, resulted in a saving of almost 8 kg on the weight of the complete car. The original weight of the insulation was 11.3 kg, but the new technology weighs only 3.4 kg."

The 8kg of weight saved is for comparison of exactly the same car model with the same construction. However, for a new clean-sheet design with the 8-kg of sound-insulation saved will result in another 8-12 kg's of weight save in the car's structural weight, suspension weight, engine weight, tire weight, etc...so the effect of weight saved in one area will have cascading effect of weight saved elsewhere in the car. A total weight saved of 16-20 kg is not at all trivial.

Don't forget about the impact of taking those software engineers away from their normal jobs and how it effects on going projects [moving resources to a new project which will require hiring audio experienced DSP software engineers along with taking existing engineers from other projects].

The costs in manufacturing are never as cut and dry as simply the "developmental cost" as human resources are typicaly more limited (time & people). Now you may be delaying the launch of a new product or firmware updates on an existing product. The strategy group has to determine if it is worthwhile to do that over just using a lightweight material.

Patrick, Roger,

Some good discussion regarding active noise cancellation in vehicles. As a side note, it is (was?) also currently used in the Acura RL in the U.S.

Patrick is right in that it takes some extra hardware and a lot more signal processing power, but something that hasn't been addressed is that it's mainly only effective at lower frequencies (<800 Hz, for sure). This is due to both a lack of processing power to tackle higher frequencies, as well as the dynamic noise characteristics inside a vehicle (including spatial variation for each passenger position).

The big advantage I see is that reducing low frequencies is actually the difficult part in vehicles and requires the heaviest materials. So there is good potential to reduce weight by adding ANC. It seems there is still a lot of work to be done to have an effective system, and adding microphones and additional DSP may or may not be cost-effective compared to spraying some asphalt on the floor of the vehicle.

Certainly ANC is a bit complicated for an entry-level model, but for luxury models, which is priced 2-3x that of entry-level, there is a lot of lattitude for a sophisticated ANC.
How can anyone put the value on the ability to squelch the noise of screaming kids, or your ______ mom-in-law? (put your favorite adjective in the blank!) Priceless! A sophisticated sound-control panel will give the ability to cut out certain voice frequency (eg. the voice of the last speaker) That would be real fun, as that person tries to yell at you and no one can hear it!

"Automakers there are looking for ways to lighten their vehicles without reducing overall safety, performance or comfort."

Wow....what a novel idea...actually ENGINEER cars to be better while making them light. Perhaps the piles of fecal crap Americans drive called SUVs will finally be designed correctly and not by some half-assed bunch of idiots who call themselves engineers who think they work for quality car companies.

Well, not to bring a dirty word like "economics" into this, but as I recall the reason the minivan and then the SUV were so popular with the manufacturers is that the were sharing a chassis with cars and trucks that had already been developed. Very few cars seem to be developed witht he luxury of a clean piece of paper (or blank CAD file). I wonder if the Chevy Volt, which seems to have started from a blank slate has this kind of weight reduction?

Today we issued the second press release in our Hitwise Holiday Series, highlighting the fact that search is driving 48% of visits to the top recipe sites as we approach Thanksgiving. I decided to take this opportunity to pull out one of my favorite charts that demonstrates the trade- off between searches for Thanksgiving Day recipes and visits to the major online dieting sites...