【作者】 安康；

【导师】 沈勇；

【作者基本信息】 南京大学 ， 声学， 2010， 博士

【摘要】 扬声器线阵列的研究与开发是当前扩声领域的一项热点。扬声器线阵列通常被设计成模仿一条连续线声源,因此具有尖锐的指向性,伴随较小的旁瓣,在近场区域的声压级随着距离加倍而衰减3dB,这一特性被我们熟知并且广泛应用于各种扩声场合。实际的应用中,扬声器线阵列并不是理想的连续线声源。这是由于它由数个独立的扬声器箱体垂直堆叠而成,而这些箱体中的扬声器不是紧密连接的。在高频时,声波复杂的干涉导致远距离投射难以实现;同时,指向性图中出现大的旁瓣,并且形态随着频率变化以及扬声器之间的声源间隙而变化,难以控制。因此有效辐射率作为扬声器线阵列的一个重要参数出现,它定义为每个箱体的有效辐射长度与箱体高度的比值。在设计中通常追求尽可能高的有效辐射率。本文介绍了点源叠加、线源积分、指向性乘积理论等这些线声源的基本分析方法,进而分析了各种常用的扬声器阵列的理论模型,并通过指向性图介绍了各自的特点。直线声源的聚焦性能好,适合远距离投射;而弧线声源覆盖角不会随着频率升高而急剧变窄,因此适合覆盖舞台近距离的听众区域;J型声源和渐进声源作为直线和弧线两种声源的结合体,兼具两种声源的优势,既实现远距离投射又兼顾近距离覆盖。而面对扬声器阵列与理想线声源之间的差距,本文提出了一种通过测量轴上频率响应差估算扬声器线阵列有效辐射率的方法,仅仅通过测量不同位置的频率响应曲线,计算得到频响差之后,可以根据其和有效辐射率之间的关系求出后者的估计值,本文对于计算频响差的近点和远点位置、区间范围进行了深入探讨。最后,本文提出一种对于扬声器线阵列高频波导排列方式的优化方法,以提高扬声器阵列的有效辐射率。由于工艺所限,扬声器线阵列的有效辐射率不易达到百分之百,而将高频波导的排列方式进行优化,可以绕过工艺方面的限制,提高有效辐射率。这种排列方式的优化所带来的水平指向性影响,又恰好可以被利用于阵列的水平指向性控制,因此是一个很巧妙的方法。实验数据表明,实测的曲线与理论计算吻合的很好,结果可信而且有很高使用价值。更多还原

【Abstract】 The research and development of loudspeaker line arrays are topics of interest in sound-reinforcement applications,as they can produce more sound power to cover a large audience area.A loudspeaker line array is designed to work as much the same as a continuous line source,which has a narrow directivity with low side lobes,and a pressure response that decreases in level at-3 dB per doubling of distance in the near field.These characteristics are valuable and have been applied in many sound-reinforcement venues.However in practical applications,a loudspeaker line array is not actually a continuous line source,because it consists of a vertical assembly of separate enclosures,and the radiating transducers do not touch each other.At high frequencies,waves with different phases lead to irregular interferences,and it becomes difficult to achieve a long distance radiation.Meanwhile side lobes appear and vary materially with both the frequency and the gap length between transducers,which is also difficult to control.As an important parameter of loudspeaker line array,Active Radiating Factor(ARF)is defined as the ratio of actual radiating length(without gaps)to the total length of each enclosure.ARF is desired to be as high as possible,so the array works as much the same as a continuous line source.This PhD thesis deals with the way how to build the model of a loudspeaker line array.Some basic principles are introduced,and several kinds of typical loudspeaker line arrays are analyzed by responses and directivity characteristics.The ARF problem is concerned in the thesis,a way of evaluating ARF by measuring on-axis frequency responses are introduced,and an optimized way of increasing ARF is also shown which deals with two types of arrangements of high-frequency waveguides by simulations and experiments.With tolerable errors,the experiment data agree well with the simulation results.更多还原