Low Frequency Noise Reduction of Small Wind Turbine
|關鍵字:||小型風力發電機;吸音材料;多孔性材料;複合材料;低頻噪音;Small wind turbine;sound-absorbing materials;composites;low-frequency noise|
In this paper, one kind of sound absorption materials is explored for low frequency noise reduction of small wind turbines. The sound absorption material is mainly made up of fiberglass fabric composite plate, air layer, and a porous foam material. Experiments of measuring the amount of sound absorption using the ASTM E1050-98 dual-microphone testing technique were performed to verify the suitability of the equation for predicting the absorption frequency of this kind of sound-absorbing material. Then use the frequency prediction equation to design different sound-absorbing material combinations. The sound pressure measurement tests for these sound-absorbing materials were performed to study their sound absorption capabilities. The design parameters for the sound absorbing materials are the thicknesses of fiberglass fabric composite plate, air layer, and the porous foam. The effects of the design parameters on the magnitude of sound absorption coefficient and bandwidth of frequency spectrum are studied through the measurement of sound absorption coefficient for the materials of different combinations. Two types of noise-reduction devices, namely circular- and L-types, made of the proposed sound absorption material are developed for low frequency noise reduction of small wind turbines. The properties of these noise-reduction devices are studied via both theoretical and experimental approaches. The results show that the circular type only has noise reduction capability in the radial direction while the L-type has noise reduction capability in both the radial and axial directions for wind turbines.