Reducing the engine noise in cars to an environmentally-acceptable standard consists in layering or stacking heavy materials, such as asphalt, on the floor of the car to absorb the sound.
But it is a weighty process, adding kilos onto the overall weight of the car, increases the power and therefore the fuel consumption needed to make it go. However, EUREKA project E! 2411 ERTAC has come up with a system to make lighter sound insulation, which reduces the car’s weight, and boosts its overall efficiency.
At the behest of French car manufacturers, EUREKA project E!2411 ERTAC set out to reduce the weight of car sound insulation by 30-50% while maintaining the same level of acoustic comfort inside the car. The project partners chose to develop new computer techniques to predict the behaviour of insulation parts made from different low mass materials. “The manufacturers drastically reduced the time schedules for new car models, so instead of using slow, time consuming experimental approach to car acoustics, we switched to developing simulation techniques using proven models to predict the behaviour of materials for sound insulation” explains Maurice Fortez, director of the main project partner, Treves.
The behaviour of the raw materials was tested for sound insulation, absorption and damping. The project found that layering compressed felt with a low density kind reduced the weight of sound insulation by 50%. Using foam textile waste to manufacture parts requiring a certain amount of elasticity reduced weight by a further 25% and diminished the cost of the insulation. Converting the results to a prototype for a real car – a Renault, gave a hefty overall car weight reduction of 6.7%.
The virtual results have gone on to be validated on another real car - the Citroen C4. “There is a saving of about 8kg on the weight of the complete car” says Fortez. “The original weight of the insulation was 11.3 kg, but the new technology weighs only 3.4kg”, he adds.
A prototype is now being manufactured at Peugeot. Fortez says “Peugeot wants to use the prototype for its new 207 model. The company is very interested in a big reduction of car weight and wants to verify the results”.
Without EUREKA support, Treves would not have been able to launch the project says Fortez. “Treves is not specialised in acoustic simulation. EUREKA really facilitated the partnership that we needed. It brought in the acoustic specialists and acoustic experts that we needed”.