在噪音控制當中，傳統被動式吸音結構若要吸收低頻噪音通常結構較為厚重且吸音頻寬較小，因此本研究想改善傳統吸音結構的缺點，主要在設計厚度小、平均吸音率高且寬頻吸音的結構。針對人耳敏感的300~3000 Hz低頻區間，利用模擬退火法對結構進行吸音率的最佳尺寸設計。本研究提出了兩種寬頻吸音結構，第一種結構是由五根分頻率區段最佳化串聯直圓管與兩根四分之一波長管並聯，將圓形截面改成長方形截面並在空間中彎折堆疊而成以降低結構厚度；第二種結構則是由四個分段頻率吸音最佳化之四分之一圓微穿孔板並聯結合，並與兩組千層派結構複合而成。
以聲學理論結合模擬退火法設計各種吸音結構(四分之一波長管、串聯管、微穿孔板)之最佳化尺寸，並使用多重物理分析軟體(COMSOL Multiphysics) 進行最佳化結構於阻抗管中的吸音率計算，並和理論預測值進行比對。其中也探討截面形狀對串聯管和千層派結構吸音特性的影響。最後，架設聲學阻抗管量測系統並以雙麥克風法進行結構的吸音率實驗量測，兩種設計結構中，微穿孔板由鋁板雷射加工製作，其餘皆以3D列印組合而成，實驗量測皆與數值模擬結果比對驗證。由數值模擬與實驗量測結果發現，由微穿孔板與千層派組合而成的第二種結構在目標頻率區間吸音效果相當好，實驗之平均吸音率達0.82。在結構厚度僅有7.15 cm下能吸收波長約為1 m的低頻噪音，可廣泛使用在室內外建築吸音。

For traditional passive sound absorbing structure to absorb low frequency noise, the structure is usually thick and has a small sound absorption bandwidth. Therefore, this study intent to improve the shortcomings of the traditional sound absorbing structure. Mainly focuses on designing sound absorbing structures with small thickness, high average sound absorption and broadband sound absorption. Aiming at the low frequency range of 300~3000 Hz, which is sensitive to human ears. The simulated annealing method is used to optimize the size of the sound absorbing structure. Two broadband sound absorbing structures are proposed in this research. The first structure consists of five serial connected straight circular tubes with the optimized frequency division section and two quarter-wavelength tubes in parallel (SA_SPT). The circular section is changed to a rectangular section and folded in space to reduce structure thickness; The second structure is composed of four parallel quarter-circle micro-perforated plates optimized with segmented frequency, and combined with two pancake structures (SA_MPP-Pan).
We design the optimized size of various sound absorbing structures (quarter-wavelength tubes, serial connected tubes, micro-perforated plates) based on acoustic theory and simulated annealing method. And calculate the sound absorption coefficient of the optimized structures in the impedance tubes with COMSOL Multiphysics, and compare with the theoretical prediction value. The influence of cross-sectional shape on the sound absorption characteristics of serial connected tubes and pancake structures is also discussed. Finally, the acoustic impedance tube measurement system is set up and the sound absorption coefficient of the structure is measured by the two microphone method. For the two design structures, the micro-perforated plate is made of aluminum plate with laser processing, and the rest are manufactured by 3D printing. The measurements are verified by comparing with the numerical simulation results. From the results of numerical simulation and experimental measurement, it is found that the second structure composed of micro-perforated plates and pancake structures has a very good sound absorption effect in the target frequency range, and the average sound absorption coefficient in the experiment is 0.82. With a structure thickness of only 7.15 cm, it can absorb low frequency noise with a wavelength of about 1 m, and can be widely used in indoor and outdoor buildings.

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