【摘要】：諧波失真是影響揚聲器音質(zhì)的一個重要因素,諧波失真的大小往往決定著揚聲器品質(zhì)的高低。其中總諧波失真、2次諧波失真和3次諧波失真是設計開發(fā)高品質(zhì)揚聲器的過程中必不可少的需要測試的物理參數(shù)。揚聲器在低頻時由于驅動力、支撐系統(tǒng)的非線性而導致的諧波失真問題已有較多的文獻在這方面做了研究,而關于揚聲器在中高頻段由于揚聲器振膜的非線性彈性振動而導致的諧波失真問題,研究文獻仍比較缺乏。碩士期間,在閱讀文獻的基礎上,主要開展了以下工作：1.推導了軸對稱旋轉薄殼的線性振動微分方程組,利用此微分方程組,結合錐形揚聲器振膜的實際幾何、材料參數(shù)和邊界條件,采用有限差分數(shù)值計算方法,計算了錐形揚聲器在線性振動情況下的共振頻率、振型函數(shù)和頻響曲線,并通過與Frankort[3]的計算結果進行對比,對本文的計算結果進行了驗證。2.根據(jù)假設振型函數(shù)法的基本思想,通過用揚聲器振膜在某一驅動頻率力下的線性響應振型函數(shù)對連續(xù)體進行離散,從Hamilton變分方程出發(fā)推導了軸對稱旋轉薄殼的非線性振動方程,給出了方程中系數(shù)的積分形式的計算表達式。3.采用多尺度法求解了非線性振動方程,得到了幅頻方程和3次近似解,說明了諧波項與非線性系數(shù)的關系。計算了特定實例下錐形揚聲器振膜的2次、3次諧波聲壓和基波聲壓的頻率響應曲線。4.通過采用數(shù)值計算方法,探討了錐體的幾何、材料參數(shù)對非線性系數(shù)的影響。并進一步通過計算錐形振膜的幾何、材料參數(shù)對振型函數(shù)的影響對計算結果進行了驗證。計算結果表明通過選擇合適的幾何、材料參數(shù),可以使諧波失真得到一定程度的減小。5.根據(jù)軸對稱旋轉薄殼的一般理論,探討分析了指數(shù)形振膜和拋物線形振膜的力學振動、聲輻射和非線性特性。
[Abstract]:Harmonic distortion is an important factor that affects the sound quality of loudspeakers. The magnitude of harmonic distortion often determines the quality of loudspeakers. The total harmonic distortion, the second harmonic distortion and the third harmonic distortion are essential physical parameters to be tested in the design and development of high quality loudspeakers. The problem of harmonic distortion caused by driving force and nonlinear supporting system in loudspeakers at low frequency has been studied in many literatures. However, the harmonic distortion caused by the nonlinear elastic vibration of loudspeakers in the medium and high frequency band is still lacking. During the master period, on the basis of reading the literature, the main work carried out the following: 1. The linear vibration differential equations of axisymmetric thin rotating shells are derived. The finite difference numerical method is used to calculate the vibration characteristics of thin axisymmetric shells by using the finite difference method, combining with the actual geometry, material parameters and boundary conditions of conical loudspeakers. The resonance frequency, mode function and frequency response curve of conical loudspeaker under linear vibration are calculated and compared with that of Frankort [3]. According to the basic idea of the hypothetical mode function method, the nonlinear vibration equation of axisymmetric rotating thin shell is derived from the Hamilton variational equation by using the linear response mode function of the loudspeaker diaphragm under a certain driving frequency force. The expression of integral form of coefficient in the equation is given. The nonlinear vibration equation is solved by multi-scale method. The amplitude frequency equation and the cubic approximate solution are obtained. The relationship between the harmonic term and the nonlinear coefficient is explained. The frequency response curves of the second and third harmonic sound pressure and the fundamental wave sound pressure of conical loudspeaker are calculated. 4. The effects of cone geometry and material parameters on nonlinear coefficients are discussed by numerical method. Furthermore, the calculation results are verified by calculating the geometry of the conical diaphragm and the influence of material parameters on the mode function. The calculation results show that the harmonic distortion can be reduced to a certain extent by selecting appropriate geometry and material parameters. Based on the general theory of axisymmetric rotating thin shell, the mechanical vibration, acoustic radiation and nonlinear characteristics of exponential and parabolic diaphragm are discussed and analyzed.
【學位授予單位】：浙江師范大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TN643

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本文編號：2361151