侷域共振聲子濾波器; Locally resonant phononic filter

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题名:	侷域共振聲子濾波器;Locally resonant phononic filter
作者:	郭中竣;Chung-Chun Kuo
贡献者:	光電科學研究所
关键词:	荷姆霍茲共振器;聲子晶體;Helmholtz resonator;phononic crystal
日期:	2011-07-13
上传时间:	2012-01-05 14:34:54 (UTC+8)
摘要:	本論文主要是研究利用聲波正向入射荷姆霍茲共振器，觀察其低頻和高頻共振頻率因為結構參數改變的變化行為，並針對高頻共振頻率，提出對應的彈簧模型，最後利用實驗量測來驗證模擬和彈簧模型的正確性。在模擬方面，利用有限時域差分法(Finite-Difference Time-Domain, FDTD)來計算出結構的穿透頻譜圖，挑選出低頻和高頻的共振頻率，再利用連續波入射結構得到速度場和壓力場圖，經由穩態場的處理，得到不隨時間改變的場圖，從該場圖中，我們觀察出在高頻共振頻率所對應的彈簧模型，比較模擬計算和彈簧模型的結果，會發現共振頻率因結構參數改變的行為是相互符合的。在量測方面，設計了兩種不同方式製作的荷姆霍茲共振器，並利用ultrasonic immersion transmission technique方式量測不同結構的穿透頻譜。比較兩種不同方式設計荷姆霍茲共振器，會發現各有其優缺點，但相同的是低頻和高頻的transmission dip在兩種結構中都有出現。對高頻共振頻率來說，量測到的強度最弱其衰減強度達到30dB，低頻的共振頻率也有20dB。這結果可以被用來設計窄頻寬的聲波濾波器。 This work demonstrates the influences of various structural parameters on resonant modes at lower and higher frequencies with the normal incidence of the Helmholtz resonators. From observing the field distribution, the spring-mass model is introduced to explain the resonant modes of the Helmholtz resonators. After, we use the measurement to show the accuracy of the simulation results and the reasonable of the spring-mass model. For the simulation, the Finite-Difference Time-Domain method is applied to calculate the transmission spectra of the Helmholtz resonators. The stable pressure and velocity fields are obtained by launching the continuous wave into the structure at lower and higher resonant frequency, respectively. From the field distributions, the comparisons of the resonant frequencies with various structural parameters between the spring-mass models and the simulation results are in good agreement. For the measurement, we design two different methods to fabricate the Helmholtz resonators. The ultrasonic immersion transmission technique is applied to measure transmission spectra of Helmholtz resonators. The transmission dips with resonant modes at lower and higher frequencies are observed in both two different types of the Helmholtz resonators. The transmission can be as low as -30dB and -27dB for the resonant modes at higher and lower frequencies, respectively. The results can be applied to the design of a narrow pass band acoustic filter.
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