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41which has a remarkably high value for the loss factor (0.8-1.0) and is distinguished by a very low compression set ( < 1%). The outstanding airborne sound insulation properties are demonstrated by measurements in a vibration room (DIN 52 212). In addition to these good physical properties, this flexible foam system also has excellent application properties. It gives a good flowability in complicated moulds. Therefore, it is highly suitable as a carpet underlayer in automobiles. THE OPTIMISATION OF ACOUSTIC POLYURETHANES USING THE COMPUTER AIDED NOISE ANALYSISW. R. Grace (Teroson) produces acoustic packages for a wide range of automotive applications throughout Europe. Teroson's approach is to offer a complete service to the automotive industry which involves a high degree of initial design and development of the final package and not simply supplying a part of a package to a given drawing. In order, to produce an optimum solution to a customer's acoustic problems that includes cost and weight effectiveness along with fit and function performance, Teroson has developed a system called &dquo;Computer Aided Noise Analysis and Simulation (CA.NA.S.).&dquo;This program uses the traditional 'Window Method&dquo; for the identification of noise sources but introduces advanced algorithms that assist in accurate simulation of a prototype vehicle's acoustic performance without the need for prolonged testing. The optimum acoustic package can then be defined within the computer environment allowing many different possible combinations to be evaluated. This provides a drastic reduction in the usually required for such testing, and the tradeoff between cost, weight, etc., can be easily and clearly portrayed to the manufacturer. The paper describes the CA.NA.S. program and gives examples of recent usage.

27of flow, such as air entrapments, porosities, welding lines, etc., the mold filling simulation is an effective tool in the early design phase. This simulation has to include the flow of the reaction mixture from the mixing head through the gating system into the mold cavity. 1b provide such a computer aided engineering software for the RIM process, a program describing the relevant physical effects has been developed. Based on the calculation of the three-dimensional flow field in complex geometries it is now possible to optimize the molding conditions in early stages, even before the production of the mold. Runner design is carried out for several types of gating systems, namely fan gate, dam gate and coathanger runner. The most important design criterions for these components are the realisation of separation-free inflow and the ensuring of a well-defined flow profile into the mold cavity in connection with minimal gate dimensions to reduce waste material. The intention is to determine the appropriate geometry of the gate, depending on molding conditions, the size of the part and the chosen RIM system.To verify the numerical results, several experiments with a model-fluid in a transparent mold for flow visualization and also with real system on RIM machines were carried out. The results show the agreement between simulation and experiments. As well as the inflow conditions, the flow inside the cavity itself is very important with reference to the quality of the resulting RIM part. With the aid of the mold filling simulation it is possible to optimize both, the gating and the mold venting position, with respect to the appearance of porosities and welding lines. In addition, for reinforced RIM parts, this simulation gives the knowledge about the filler particle orientation. THE