Simulation of Noise Reduction in Passenger Trains Using Metal Foams 2011-01-1637
One of important problems in railway transportation systems is control of noise and vibration. Metal foams are very good medias for absorbing noise. So in this paper, noise of motion of a train is simulated by MATLAB software and the reduction of noise level in a compartment of passenger car that is equipped by metal foam sheets is considered. Commonly, the sound absorption coefficients are obtained experimentally and they are available in datasheets and references.
The different parameters that influence on the capability of this equipment were considered. For example the microstructure, thickness, magnitude of compaction, relative density and etc of metal foam is effective parameters. High porosity has good effect on the performance of absorber sheet. By increasing of compaction ratio, in frequency domain we will have enhancing of absorption of the noise. Compaction process is done by two different ways: one is direct and else is progressively. Relative density has inverse relation with reduction of sound pressure level. So with these considerations the absorption ability of metal foams is less than glass wool as one of the best available noise absorbers in industry. But by changing the microstructure such as rolling, compaction and derailment and also increasing area of used metal foam, we can achieve to high level performances.