Standards have limited the allowable noise levels in different situations, requiring the study of solutions at the source, in the path or the receiver. Muffler is the major factor influencing the noise of rotary compressor. Control and analyze the acoustic characteristics of muffler is essential. Porous materials have been studied and widely applied to reduce aircraft and vehicular noise or industrial problems in general. Generally, designers use absorbing materials available on the market, however they are not always adequate to the problem when there is the presence of another gas, for example in hermetic compressors. Thus it is proposed to model the propagation in rigid porous material, characterize and develop the porous metal optimizing your acoustical absorption performance, when applied in a cavity. Direct techniques for measuring the material properties such as resistivity, porosity, tortuosity and characteristic thermal and viscous length will be studied.
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