Tanaka Nobuo, Tanaka Motoki
Department of Aerospace Engineering, Tokyo Metropolitan University, 6-6 Asahigaoka, Hinoshi, Tokyo 191-0065, Japan.
J Acoust Soc Am. 2010 Jun;127(6):3526-37. doi: 10.1121/1.3409483.
Arguably active noise control enables the sound suppression at the designated control points, while the sound pressure except the targeted locations is likely to augment. The reason is clear; a control source normally radiates the sound omnidirectionally. To cope with this problem, this paper introduces a parametric array loudspeaker (PAL) which produces a spatially focused sound beam due to the attribute of ultrasound used for carrier waves, thereby allowing one to suppress the sound pressure at the designated point without causing spillover in the whole sound field. First the fundamental characteristics of PAL are overviewed. The scattered pressure in the near field contributed by source strength of PAL is then described, which is needed for the design of an active noise control system. Furthermore, the optimal control law for minimizing the sound pressure at control points is derived, the control effect being investigated analytically and experimentally. With a view to tracking a moving target point, a steerable PAL based upon a phased array scheme is presented, with the result that the generation of a moving zone of quiet becomes possible without mechanically rotating the PAL. An experiment is finally conducted, demonstrating the validity of the proposed method.
可以说，有源噪声控制能够在指定控制点实现声音抑制，而目标位置之外的声压可能会增大。原因很明显；控制源通常会全向辐射声音。为了解决这个问题，本文介绍了一种参量阵扬声器（PAL），由于其使用超声波作为载波的特性，它能产生空间聚焦声束，从而使人们能够在指定点抑制声压，而不会在整个声场中产生溢出。首先概述了PAL的基本特性。然后描述了由PAL源强度在近场中产生的散射压力，这是有源噪声控制系统设计所必需的。此外，推导了使控制点声压最小化的最优控制律，并通过分析和实验研究了控制效果。为了跟踪移动目标点，提出了一种基于相控阵方案的可控PAL，结果是无需机械旋转PAL就可以产生一个移动的安静区域。最后进行了实验验证了所提方法的有效性
