Vibroacoustic attenuation effect of sandwich damping material on pipe flow noise

Abstract

Normally, pipe flow noise is generated by the fluctuation of pipe entrained fluid excited by sources in the fluid such as pumps and the vibration of pipe wall excited by mechanical connections to a vib rating machine. Thus, potentially many different types of wave could exist within a pipe structure and the entrained fluid. To attenuate such kind noise, damping materials, such as rock wool, glass wool, PE (poly ethylene), PU (poly urethane), can be used to sheathe the pipe wall to absorb or isolate the pipe flow noise. For the purpose to raise the effectiveness of noise reduction, a number of sandwich materials like PE+lead sheet, glass wool+aluminum foil etc., are considered. In this paper, comparative study by numerical simulation of the sound field around pipe wall and the vibration of pipe wall are carried out by BEM and FEM. In which, the modeling technique of contact elements between pipe wall and damping material or inter-sandwich materials are explained. Complementary experimental technique based on Fuglsang Nielsen's method for measuring loss factor of damping material are also described. Both analysis and experiment results show that the sandwich damping materials can further reduce the radiated pipe flow noise by an amount of 12-15 dB than that using pure sound absorptive material for pipe sheathing.