Poletti Mark A, Betlehem Terence, Abhayapala Thushara D
Callaghan Innovation, P.O. Box 31-310, Lower Hutt, New Zealand.
Research School of Engineering, Australia National University College of Engineering and Computer Science, The Australian National University, Canberra, Australia.
J Acoust Soc Am. 2014 Jul;136(1):192-200. doi: 10.1121/1.4883363.
Higher order sound sources of Nth order can radiate sound with 2N + 1 orthogonal radiation patterns, which can be represented as phase modes or, equivalently, amplitude modes. This paper shows that each phase mode response produces a spiral wave front with a different spiral rate, and therefore a different direction of arrival of sound. Hence, for a given receiver position a higher order source is equivalent to a linear array of 2N + 1 monopole sources. This interpretation suggests performance similar to a circular array of higher order sources can be produced by an array of sources, each of which consists of a line array having monopoles at the apparent source locations of the corresponding phase modes. Simulations of higher order arrays and arrays of equivalent line sources are presented. It is shown that the interior fields produced by the two arrays are essentially the same, but that the exterior fields differ because the higher order sources produces different equivalent source locations for field positions outside the array. This work provides an explanation of the fact that an array of L Nth order sources can reproduce sound fields whose accuracy approaches the performance of (2N + 1)L monopoles.
第N阶的高阶声源能够以2N + 1种正交辐射模式辐射声音，这些模式可以表示为相位模式，或者等效地表示为幅度模式。本文表明，每个相位模式响应都会产生具有不同螺旋速率的螺旋波前，因此声音的到达方向也不同。因此，对于给定的接收器位置，高阶声源等效于由2N + 1个单极子源组成的线性阵列。这种解释表明，类似于高阶源圆形阵列的性能可以由源阵列产生，其中每个源由在相应相位模式的视在源位置处具有单极子的线阵列组成。文中给出了高阶阵列和等效线源阵列的仿真结果。结果表明，两个阵列产生的内部场基本相同，但外部场不同，因为高阶源为阵列外部的场位置产生了不同的等效源位置。这项工作解释了这样一个事实，即L个第N阶源的阵列可以再现声场，其精度接近(2N + 1)L个单极子的性能。
