耳機聲學最佳化設計與全向性聲源設計

Abstract

面對耳機設計時各種相互衝突的特性需求，如靈敏度、失真率、頻寬以及微小化等，需要一種有系統且有效率的方法來達成我們的設計並符合設計需求。 利用微型揚聲器的參數鑒別法、電機聲模擬電路 (EMA)，建立耳機的聲學模擬平台。並且以此平台為基礎，利用模擬退火法 (simulated annealing)進行耳機腔體的最佳化設計，並能有效達到期望目標。實驗方面，利用Type 3.3人工耳（IEC 711 ear simulator）來得到實驗結果，並且顯示出經最佳化後的耳機腔體設計，能夠大大的提升其聲學品質，並且能夠符合3GPP2的規範。 全向性聲源在某些特定的聲學測量和音訊重現應用中是有需要的，在本篇論文中，把十二個動圈式喇叭分別鑲嵌到鋁製正十二面體的十二個面上，形成一個十二面體揚聲器來近似全向性聲源。為了預測指向性，利用等效聲源法(ESM)來建構此十二面體揚聲器的模型，利用此模型來模擬遠場聲壓，實際上的量測，是採用旋轉桌(turn table)量測水平面3600的聲壓分佈，由實驗跟模擬上的結果，可以顯現出此正十二面體揚聲器的性能，非常接近全向性聲源。

Faced with various conflicting issues arising from sensitivity, distortion, bandwidth and miniaturization requirements for earphones, it is desirable to develop a systematic way to attain the design that would meet these requirements. Based on a lumped parameter model, the design of the earphone enclosure is optimized using the simulated annealing (SA) algorithm. Experimental results obtained using a type 3.3 artificial ear (IEC 711 ear simulator) reveals that the optimized design has resulted in significant enhancement of performance, complying with the frequency response mask dictated in the 3GPP2 standard. Omni-directional sources are required in some special acoustical measurements as well as audio reproduction applications. This thesis aims to design a dodecahedral loudspeaker source to approximate an omni-directional source. Twelve drivers are mounted in an enclosure made of stainless steel. In order to predict the directional response, the equivalent source method (ESM) is employed to calculate the pressure radiation pattern of the source. In addition to the numerical simulation, practical measurement of the directional response was performed using the turn table. Both numerical and experimental results show demonstrated the satisfactory omni-directional property of the source.