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Title: | 雙模態費諾可透氣式超穎材料應用於寬頻聽覺濾波 Dual-mode Fano ventilated metamaterials for wideband auditory filtering |
Authors: | Xi-Wen Xiao 蕭翕文 |
Advisor: | 劉建豪(Chien-Hao Liu) |
Keyword: | 費諾共振器,噪音降低,共振耦合,聲音濾波,可透氣式聲學超穎材料,寬頻濾波器, Fano resonator,noise reduction,resonant coupling,sound filtering,ventilated acoustic metamaterials,wideband filters, |
Publication Year : | 2020 |
Degree: | 碩士 |
Abstract: | 可透氣式聲學超穎材料在低頻聲音濾波和流體可通透等性質上吸引許多研究關注。在本研究中,提出一具備寬頻濾波和有效率通氣特性、基於雙模態費諾共振器和耦合機制進行設計的圓柱形聲學超穎材料。每一單元由一個可提供穩定流體通過、位於中心的共振區域與環繞其周圍之六個螺旋通道的共振區域所組成,以在遠場區域產生聲波的破壞性干涉現象。有別於傳統單費諾共振類型的超穎材料,可調整前兩個費諾共振頻率,來形成相對寬頻之帶阻濾波響應特性,再藉由將兩個費諾共振器耦合,來得到更寬頻的隔音表現。此種設計的優點為較少的耦合單元形成之橫向、縱向緊密的尺寸與結構透氣性。透過簡化之等效電路模型與有限元素模擬可設計出一由兩個雙模態費諾共振單元所組成的架構,並達成至少89% 的10 dB比例頻寬(即90% 以上的聲能被過濾)與33.4% 空氣流通率表現。設計結構之樣品採用3D列印進行製作,再以阻抗管實驗量取其特性。此研究提出之方法可延伸應用於多費諾共振器的耦合來達成極寬頻,而本研究成果也預期可以有益於在聲音濾波、管道噪音減低以及有限體積空間的相關應用。 Ventilated acoustic metamaterials have attracted considerable attention for their capabilities of low-frequency sound filtering and fluid ventilation. In this research, we modified a cylindrical acoustic metamaterial with wideband auditory filtering and efficient air ventilation, which were based on dual-mode Fano resonators and coupling mechanisms. Each unit consists of a non-resonant opening region in the center as a passage for steady air flows and a surrounding resonant region with six helical air channels for creating destrcutive interference of sound waves in the far field region known as Fano resonances. In contrast to conventional single-Fano-resonance metamaterials, the first two modes of the modified dual-mode Fano resonator can be manipulated to provide a relatively wide stopband filtering response. By coupling multiple Fano resonators appropriately, the bandwidth of stopband can be increased further to provide a wide soundproofing range. The advantages of the newly modified structures include efficient ventilation and compact size in the lateral and longitudinal directions due to fewer coupled elements. A two-element dual-mode Fano metamaterial we modified could achieve a 10 dB fractional bandwidth of 89% at least (i.e. 90% of sound energy was filtered out) and an air passage rate of 33.4% through a simplified equivalent circuit model and finite element simulations. A prototype is fabricated with 3D printing and experimentally characterized by an impedance tube. The proposed approach can be extended to multiple coupled Fano resonators for ultra-wide bandwidths. The research results are expected to be beneficial for sound filtering and noise reductions in duct applications and spaces with limited volume. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/62716 |
DOI: | 10.6342/NTU202000938 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 機械工程學系 |
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File | Size | Format | |
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ntu-109-1.pdf Restricted Access | 30.77 MB | Adobe PDF |
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