微型喇叭於智慧型行動裝置之聲腔設計與測試研究

微型揚聲器之交流阻抗常會因為測試方法的不同，得到不同的阻抗特性曲線，影響T&S參數的計算，使頻率響應曲線的模擬出現了變化。定電流與定電壓的試驗選擇，是目前常用的測試技術之一，但也使喇叭的阻抗測試上充滿了許多變數。微型揚聲器於實際電路應用上是使用一定的功率驅動，使其動作上達到特定的能力。測試電壓的不同，亦使揚聲器的阻抗產生不同的變化，致其產生線性與非線性的特性。本文的重點即為探討喇叭阻抗特性於不同量測方法之分析及利用不同電壓測試其阻抗與頻率-聲壓線性能力。然而不同電壓所算取出的T-S參數，用電-機-聲類比電路，模擬頻率-聲壓特性曲線與實測驗證比對，並以振膜之模態分析找出問題發生的可能性。由於微型揚聲器整合於智慧行動裝置內，內部機構空間與外觀形狀設計不同，所應用的前音腔與後音箱的尺寸與容積也不同，再探討後音箱容積、前音腔容積、前音腔與後音箱整合、前音腔出音孔形狀與開孔率、後音箱不同材質與壁厚之不同變化分析，模擬頻率-聲壓特性曲線，並以實測方式驗證比對。

關鍵字

微型喇叭；線性分析；模態分析；聲腔設計；聲腔結構

並列摘要

Impedance curves of a micro-speaker are not the same for different test methods. It influences the calculation of T-S parameters which are used to simulate the frequency response curve of a micro-speaker. Constant current testing and constant voltage testing are two common test methods for AC impedance measurement. Actually, the micro-loudspeaker in the circuit is driven by required power which let micro-speaker to achieve the specific capability. But different driving voltages cause the impedance of the loudspeaker varied which induces nonlinear characteristics. The purpose of this paper is to investigate impedance properties of a loudspeaker by using different testing methods, and also to study the linear capability of impedance and sound pressure frequency response at different experiment voltages. Measured sound pressure frequency response curves are compared with simulations from equivalent circuit method by using T-S parameters measured at different voltages. The differences between simulation and measured data are interpreted with the modal analysis of diaphragm. The micro-loudspeakers usually want to integrate into the smart mobile device, because internal structure of space and exterior covering of shape design different, to affect applications are also different chamber volume. Therefore, the different back and front chamber of volumes, housing holes, materials and thicknesses, using EMA analog circuit are analyzed by the experiment and simulation result.

並列關鍵字

micro-speaker ； linearity ； modal analysis ； cavity design ； cavity structure

參考文獻

[18] 賀仁萱，以結構設計優化壓電式喇叭音頻響應的研發，碩士論文，台灣大學工程科學及海洋工程學研究所，台北，2007。

[19] 許文馨，微型喇叭之輸出分析及品質改善之研究，碩士論文，台灣大學工程科學及海洋工程學研究所，台北，2009。

[5] Richard H. Small, “Close-Box Loudspeaker Systems - Part I : Analysis,” Journal of The Audio Engineering Society, vol. 20, no.10, 1972, pp. 798-808.

[6] Richard H. Small, “Close-Box Loudspeaker Systems - Part II : Synthesis,” Journal of The Audio Engineering Society, vol. 21, no.1, 1973, pp. 11-18.

[7] Richard H. Small, “Vented-Box Loudspeaker Systems - Part I : Small-Signal Analysis,” Journal of The Audio Engineering Society, vol. 21, no.5, 1973, pp. 363-372.

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微型喇叭於智慧型行動裝置之聲腔設計與測試研究

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