小型風力發電機之低頻減噪裝置設計

Abstract

本文主要探討小型風力發電機之低頻噪音減噪裝置的吸音材料與架構。減噪裝置的吸音材料主要由玻纖布、空氣層、多孔性材料所組合而成。透過測量材料的吸音係數量測實驗(ASTM E1050-98:雙麥克風實驗)驗證吸音材理論的合用性，再利用吸音材理論設計不同吸音材的組合，進行不同吸音材組合之聲壓量測實驗。吸音材參數為玻纖布的重量、空氣層的厚度以及多孔性材料的厚度，比較參數值的不同，了解各參數對於減噪程度的大小與頻寬影響。減噪裝置外框架構的構想是將其包覆在小型風力發電機外圍，外框架構設計分為圓型與L型，進行兩種外框的聲壓量測實驗以及電扇模擬風機噪音之實驗量測，分別探討在小型風力發電機的徑向與軸向的減噪效果。結果顯示圓形外框只在徑向有減噪效果，L型外框在徑向與軸向皆有減噪效果。

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.