臺灣博碩士論文加值系統

隨著科技持續的進步與發展，人們對於揚聲器等產品的品質要求愈來愈高，尤其以電聲產業近年來的迅速發展，使電聲產品朝向輕薄短小，並針對攜帶方便的特點為發展方向。盡管揚聲器的作動原理相當簡單，但也是一項歷久彌新的技術，要生產具備好音質又低失真的完美揚聲器，卻是個極為艱鉅的任務，況且對聲音的偏好亦因人而異，因此如何生產出能滿足不同使用者需求的揚聲器，絕對是個值得投入心力研究的課題。
本文針對振膜與導音管材料結構對於揚聲器系統動態特性的影響分析與量測作深入探討，內容主要分為兩個部份，首先是研究關於音膜材料之機械特性，主要藉由實驗量測的方式，並設計夾具提供良好的邊界條件，以奈米壓痕與氣壓推動試驗分別測量不同厚度、材料的音膜之彎曲剛性，且以雷射位移計量測音膜的動態時域訊號，藉由振動學原理求得不同頻率下不同厚度、材料之阻尼比。
第二部份將針對低音反射式音箱產生寬帶噪音的問題進行實驗量測與特性分析，首先找出因系統影響導致風切音強度較強之頻帶，並以此為激振頻率，再以有限元素軟體模擬不同管徑、長度下的風切音強度，進而得到設計導音管的大方向，再以實驗驗證有限元素軟體的正確性，並比較不同尺寸導音管之實驗量測、模擬、駐波理論之共振頻，最後改變導音管的幾何結構，分別以有限元素軟體預測及實驗驗證，試圖找出有效將低風切音強度的方法。

With the continuous improvement and rapid development of technology, the demand for high quality of loudspeaker are increased. Electro-acoustic industry particularly focus on the development of speakers, to make products much smaller, thinner, and easy to carry. Though the working principle of speakers is considerably uncomplicated and the technology of speakers has been developed for a long time. However manufacturing a high-quality speaker with sweet-sounding voice and low distortion is still a difficult issue. Preference for voice is distinct for people, thus the task about designing a perfect speaker to satisfy different users is worthy of being discussed.
The main purpose of this research focuses on theoretical analysis, numerical analysis and experimental measurements on the influence of dynamic characteristics for diaphragm, and port in loudspeaker system. The content of this thesis is divided into two parts. The content of this thesis is ranged into two parts. The first topic of this thesis is to
The first topic of this thesis is to research the mechanical characteristics of materials for diaphragms by experimental measurement, and design fixtures to provide fine boundary condition. The stiffness of the diaphragm is measured by the Nano-indentation and air pressure pushing of the thin film for diaphragms. The damping ratio of the diaphragm in distinct exciting frequency is determined by measuring the dynamic signals of the different thickness and material of diaphragm on the basis of vibration theory by laser displacement sensor.
The second topic of this thesis is to perform the analysis to appraise the characteristics of broad-band noise generated from small bass-reflex loudspeaker. To begin with, we find the Bandwidth with stronger noise from system to obtain exciting frequencies. The noise strength of different diameter and length for port by the finite element analysis, consequently we can get principal direction to design port. Furthermore, the correctness of simulation is verified by experiment. We compare resonant frequency of chuffing for different port by experiment, simulation and standing wave theory. Finally, we change the shape of port to attempt to reduce the noise strength.by above-mentioned step.

摘要 I
Abstract IV
目錄 VI
表目錄 X
圖目錄 XIII
第一章 緒論 1
1.1 研究動機 1
1.2 文獻回顧 2
1.3 論文內容簡介 3
第二章 圓形開口管共振頻率與截止頻率理論 6
2.1 動圈式揚聲器結構與作動原理 6
2.2 基本聲學 6
2.2.1 聲波方程式 7
2.2.2 全向性球面波 7
2.2.3 簡單球狀聲源 8
2.3 圓形開口導音管之共振頻推導 10
2.3.1 圓形平板活塞之輻射聲壓方程式 10
2.3.2 圓形平板活塞之輻射阻抗 10
2.3.3 導音管之共振頻率推導 12
2.4 圓形開口導音管之方向性探討 14
2.4.1 線聲源聲壓之推導 14
2.4.2 圓形平板活塞遠場聲壓之推導 15
2.4.3 圓形平板活塞Beam Pattern之探討 16
2.5 圓形開口管之截止頻率 17
2.6 圓形開口導音管之理論與模擬 17
2.6.1 圓形開口管之共振時之表現 17
2.6.2 圓形開口管之方向性模擬 18
2.6.3 圓形開口管之截止頻率模擬 18
第三章 實驗量測技術與儀器設備 36
3.1 奈米壓痕試驗機 36
3.2 高精度壓力計 36
3.3 雷射位移計 36
3.4 動態機械分析儀 37
3.5 表面3D輪廓量測儀 37
3.6 CT電腦斷層掃描儀 37
3.7 光固化3D印表機 38
3.8 全無迴響室 38
3.9 CLIO電聲量測系統 39
3.10 動態信號分析系統 39
3.10.1. 振動噪音頻譜分析儀 39
3.10.2. 資料擷取卡 40
3.10.3. 動態訊號分析儀 40
3.11 PCB麥克風 41
3.12 函數產生器 41
3.13 功率放大器 41
第四章 耳機音膜彎曲剛性與阻尼比之實驗量測 52
4.1 治具與音膜 52
4.2 音膜彎曲剛性之實驗量測 55
4.2.1 奈米壓痕試驗機之實驗原理與架設 55
4.2.2 奈米壓痕試驗之音膜彎曲剛性之量測結果與數據分析 56
4.2.3 氣壓推動音膜之實驗原理與架設 57
4.2.4 氣壓推動音膜之音膜彎曲剛性之量測結果與數據分析 59
4.3 平面音膜應力應變曲線之實驗量測 61
4.3.1 動態機械分析儀拉伸試驗之實驗原理與架設 61
4.3.2 動態機械分析儀拉伸試驗之量測結果與數據分析 61
4.4 不同頻率下的音膜阻尼比之實驗量測 62
4.4.1 實驗原理與架設 62
4.4.2 不同頻率下的音膜阻尼比之量測結果與數據分析 64
4.5 以工業用3D電腦斷層掃描儀量測成形音膜之局部厚度 66
4.5.1 實驗原理與架設 66
4.5.2 量測結果與數據分析 66
4.6 小結 67
第五章 低音反射式音箱之風切音特性分析與量測 130
5.1 量測系統簡介 131
5.1.1 單體選用之原因與介紹 131
5.1.2 量測系統之原理與介紹 131
5.2 風切音量測之實驗架設 131
5.3 使用全無迴響室之原因與介紹 132
5.4 系統頻率響應及選定激振單體之頻率範圍 132
5.4.1 系統本身之音壓曲線 133
5.4.2 系統之阻抗曲線 133
5.4.3 風切音之強度比較 133
5.5 有限元素法模擬分析 134
5.5.1 COMSOL之音場可視化及修正長度 134
5.5.2 COMSOL之風切音膜擬設定 136
5.5.3 COMSOL之風切音膜擬結果與探討 137
5.6 以實驗驗證不同尺寸間風切音的強度比較 138
5.7 改變導音管尺寸之共振頻率探討 139
5.7.1 不同尺寸之導音管共振頻率比較 139
5.7.2 大口徑導音管之修正長度探討 140
5.8 以掃頻方式量測不同尺寸導音管的共振頻率 140
5.9 風切音之優化 141
5.9.1 如何改變導音管的外形 142
5.9.2 模擬不同外型之導音管對風切音之影響 142
5.9.3 以實驗驗證不同外型之導音管對風切音之影響 143
5.9.4 導音管加裝Helmholtz Resonator對風切音之影響 144
5.10 小結 146
第六章 結論與未來展望 338
6.1 結論 338
6.2 未來展望 339
參考文獻 341

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