臺灣博碩士論文加值系統

本文主要探討雙激振系統下聲壓曲線的影響，一方面藉由增加激振器數目提高激振力，提升其聲壓感度；另一方面藉改變雙激振器的激振位置來改善其聲壓曲線的平滑性。研究方法分為三部份，第一部份為用Rayleigh-Ritz method分析揚聲板的振動行為，將揚聲系統簡化成數學模型進行模擬可獲得合理的結果，並可大幅度減少計算時間，在此使用矩形複合材料平板來模擬揚聲板，用彈簧來模擬懸邊，用四根梁來模擬一個音圈，複合材料平板使用古典積層板理論，梁的部分則採用簡易梁理論。首先推導出揚聲板、懸邊及音圈的動能及應變能，用Rayleigh-Ritz method將板及梁之變形以級數方式表示，建立此揚聲系統之總勢位能，並對其變形函數未定係數變分，可求得振動特徵方程式，求解此方程式後可得到板之自然頻率、模態，進而求得聲壓曲線，再將結果與有限元素分析軟體ANSYS及實驗結果相互比較以驗證此種方法的正確性。第二部分利用有限元素分析軟體ANSYS分析各種不同激振位置下的聲壓曲線，並探討聲壓曲線的差異。最後改變揚聲板的材料常數進行聲壓分析，觀察不同材料常數下聲壓曲線的變化，以作為實務上雙激振系統平面揚聲器選擇不同材料揚聲板之參考依據。

This thesis studies the sound radiation of strip-type flat plates excited at different locations. The purpose of exciting the plate at different locations is two-fold: Raise the sound pressure level (SPL) and improve the smoothness of the SPL curve. This study consists of three parts. In the first part, a Rayleigh-Ritz method is constructed to study the vibration of sound radiation plates which comprising a flat plate, a flexible surround, and a number of voice coils. In the mathematical model of the sound radiation plate, the vibration of the plate is formulated on the basis of the classical lamination theory. The flexible surround is treated as spring. The voice coils are modeled by simple beams. The accuracy of the method is verified by the finite element code ANSYS. In the second part, the vibration response of the plate is used in the first Rayleigh integral to construct the SPL curve of the plate. The experimental SPL curves as well as those obtained using ANSYS are used to validate the suitability of the present method for the analysis of sound radiation plates. Finally, the effects of excitation locations on the SPL curves of sound radiation plates are studied. The more appropriate locations of the voice coils are determined to minimize the magnitude of the sound pressure level drop in the mid-frequency range for the plates. The effects of the material constants of the sound radiation plates on the SPL curves are also studied theoretically. The results obtained in this thesis should be useful for the design of flat-panel speakers.

第一章 緒論..........................................................1
1.1前言............................................................1
1.2文獻回顧........................................................3
1.3研究方法........................................................4
第二章 複合材料三明治板的振動分析與聲壓計算..........................5
2.1複合材料古典平板與簡易梁理論....................................5
2.1.1複合材料古典平板理論........................................5
2.1.2簡易梁理論..................................................5
2.2基層平板部分....................................................6
2.2.1平板的位移場與應變..........................................6
2.2.2平板的應力與應變關係........................................6
2.2.3平板的應變能與動能..........................................7
2.3附加於平板上之梁部分...........................................11
2.3.1梁位移場與應變.............................................11
2.3.2梁應力與應變關係...........................................11
2.3.3梁的應變能與動能...........................................11
2.4平板邊界彈性支撐的應變能.......................................16
2.5瑞雷－里茲法與特徵值、特徵向量.................................17
2.6音圈偏移一距離之勁度與質量矩陣.................................23
2.7比例阻尼下之位移向量...........................................27
2.8聲壓...........................................................28
第三章 有限元素分析.................................................29
3.1 ANSYS有限元素模型之建立.......................................29
3.1.1懸邊模型建立….............................................29
3.2 ANSYS模擬分析中各參數的取得...................................31
3.2.1材料常數的給定.............................................31
3.2.2質點元素的參數.............................................31
3.2.3彈簧元素的參數.............................................31
3.2.4激振力的給定...............................................31
3.2.5阻尼比的給定...............................................32
第四章 製作及實驗程序...............................................34
4.1平面揚聲器之各項組件製作.......................................34
4.1.1複材揚聲板之製作...........................................34
4.1.2長圓形音圈之製作...........................................34
4.1.3長圓形激振器之製作.........................................34
4.1.4懸邊之製作.................................................35
4.2平面揚聲器之組裝...............................................36
4.3揚聲器各項實驗程序.............................................36
4.3.1阻尼量測實驗...............................................36
4.3.2聲壓量測實驗...............................................37
4.3.3阻抗量測實驗...............................................37
4.3.4單體參數量測實驗...........................................38
第五章 理論分析與實驗結果...........................................39
5.1 Shell與beam元素比較...........................................39
5.2 Ritz method求解揚聲板自然頻率與模態...........................39
5.3實驗跟分析聲壓曲線比較.........................................40
5.4雙音圈系統激振位置改變對聲壓的影響.............................41
5.5材料常數對不同激振系統聲壓曲線影響.............................43
第六章 結論與未來研究方向...........................................44
6.1結論...........................................................44
6.2未來研究方向...................................................45
參考文獻............................................................46

[1]J.N. Reddy, “Nonlocal nonlinear formulations for bending of classical and shear deformation theories of beams and plates” , International Journal of Engineering Science, vol.48,pp1507–1518, 2010.
[2]H. Matsunaga, “Free vibration and stability of angle-ply laminated composite and sandwich plates under thermal loading”, Composite Structures vol.pp.77249–77262, 2007.
[3]R. D. Mindlin , “Influence of Rotatory Inertia and Shear Deformation on Flexural Motion of Isotropic Elastic Plates” , J. Applied Mechanics , vol.18 , pp.33-38 , 1951.
[4]S. T. Mau , “A Refined Laminated Plate Theory” , Journal of Applied Mechanics , vol.40(2) , pp.606-607 , 1973.
[5]P. M. Morse, and K. U. Ingrad , “Theoretical Acoustics” , McGraw-Hill , NY , 1968 ; rpt. Princeton University Press , NJ , pp.375-379 , 1986.
[6]T. Shindo , O. Yashima , H. AndSuzuki , “Effect of Voice-Coil and Surround on Vibration and Sound Pressure Response of Loudspeaker Cones” , Journal of the Audio Engineering Society , vol.28 , n 1 , pp.31-51 , 1997.
[7]E. Hojan , M. Wojtczak , M. Niewiarowixz , “Computer Simulation of SPatial Characteristics of a Loudspeaker System” , Applied Acoustics , vol.32 , pp.179-191 , 1991.
[8]H. H. Kanematsu, Y. Hirano and H. Iyama, “Bending and vibration of CFRP-faced rectangular sandwich plates”, Composite Structures, vol.10, pp.145-163, 1988.
[9]C.R. Lee, T.Y. Kam, “Identification of mechanical properties of elastically restrained laminated composite plates using vibration”, Journal of Sound and Vibration vol.295,pp.999-1016, 2006.
[10]D. Zhou., T.J. Ji, “Free vibration of rectangular plates with continuously distributed spring-mass”, International Journal of Solids and Structures vol.43, pp.6502–6520,2006.
[11]M.H. Hsu, “Vibration analysis of orthotropic rectangular plates on elastic foundations”, Composite Structures, vol.92(4) , pp.844-852 , 2010.
[12]Y.K. Cheung,D. Zhou, “Vibrations of rectangular plates with elastic intermediate line-supports and edge constraints”, Thin-Walled Structures,vol.37(4) , pp.305-331 , 2000.
[13]L. Feng , “Active Control of Structurally Radiated Sound Using Multiactuator Method” , Journal of the Acoustical Society of America , vol.98 , pp.397-402 , 1995.
[14]Y. Qiao , Q. Huang , “The Effect of Boundary Conditions on Sound Loudness Radiated from Rectangular Plates” , Archive of Applied Mechanics , vol.77 , pp.21-34 , 2007.
[15]Y.C. Huang, “Sound Radiation of Composite Flat-Plate Excited by Rectangular Transducer”, A Thesis Submitted to Institute of Mechanical Engineering College of Engineering National Chiao Tung University , Hsinchu,2009 .
[16]H.S. Wei, “Sound Radiation of Long Flat-Plate Excited by Multi-Location”, Thesis Submitted to Institute of Mechanical Engineering College of Engineering National Chiao Tung University , Hsinchu,2010 .