Université Pierre et Marie Curie, Centre National de la Recherche Scientifique, UMR-7190 - Institut Jean le Rond d'Alembert, 2 place de la Gare de Ceinture, 78210 Saint-Cyr l'Ecole, France.
J Acoust Soc Am. 2011 Sep;130(3):1325-36. doi: 10.1121/1.3605528.
Compact spherical loudspeaker arrays can be used to provide control over their directivity pattern. Usually, this is made by adjusting the gains of preprogrammed spatial filters corresponding to a finite set of spherical harmonics, or to the acoustic radiation modes of the loudspeaker array. Unlike the former, the latter are closely related to the radiation efficiency of the source and span the subspace of the directivities it can produce. However, the radiation modes depend on frequency for arbitrary distributions of transducers on the sphere, which yields complex directivity filters. This work focuses on the most common loudspeaker array configurations, those following the regular shape of the Platonic solids. It is shown that the radiation modes of these sources are frequency independent, and simple algebraic expressions are derived for their radiation efficiencies. In addition, since such modes are vibration patterns driven by electrical signals, the transduction mechanism of compact multichannel sources is also investigated, which is an important issue, especially if the transducers interact inside a shared cabinet. For Platonic solid loudspeakers, it is shown that the common enclosure does not lead to directivity filters that depend on frequency.
紧凑型球形扬声器阵列可用于控制其指向性图案。通常，这是通过调整与有限数量的球谐函数或扬声器阵列的声学辐射模式相对应的预编程空间滤波器的增益来实现的。与前者不同的是，后者与源的辐射效率密切相关，并涵盖了它可以产生的指向性子空间。然而，对于球面上任意分布的换能器，辐射模式随频率而变化，从而产生复杂的指向性滤波器。这项工作侧重于最常见的扬声器阵列配置，即遵循柏拉图立体形状的规则。结果表明，这些声源的辐射模式与频率无关，并推导出了它们辐射效率的简单代数表达式。此外，由于这些模式是由电信号驱动的振动模式，因此还研究了紧凑型多通道源的转换机制，这是一个重要的问题，特别是如果换能器在共享外壳内相互作用的话。对于柏拉图立体扬声器，结果表明常见的外壳不会导致依赖于频率的指向性滤波器。
