Adaptive Resonant Mode Active Noise Control

Low frequency sound waves propagating in a duct is ideally suited for active noise control(ANC) applications. Unlike passive treatments, ANC utilizes an acoustic actuator (loudspeaker)to cancel unwanted sound fields. There are two main control topologies whenconsidering the active suppression of sound, feedforward and feedback. The former requiresthat the disturbance be known before the control signal is generated, and is ideal for periodicor random signals. Feedback arrangements, on the other hand, modify the dynamics of anenclosured sound field to augment damping, and requires no a priori knowledge of the disturbance.A modified version of feedback that is used in structures called positive positionfeedback (PPF), can be applied to acoustic systems. In a previous study, a tuned resonantfilter modelled after a Helmholtz resonator was used in PPF configuration to suppress noiselevels by Bisnette and Vipperman (2004). However, the presence of speaker dynamics necessitatesfurther phase compensation, which is accomplished with an all-pass filter. The workpresented here further develops this control method by using a higher-order compensator. Inthis study, band-pass filters are used to improve the multi-modal control by limiting phaseinteraction of adjacent modes. Further refinements are made by realizing the control systemelectronically, which gives the ability to adapt controller parameters. Here, an algorithmis presented that adapts the resonant controller gain. Experimental results show moderatereductions with no energy spill-over to the next adjacent uncontrolled mode.

在管道中传播的低频声波非常适合用于有源噪声控制（ANC）应用。与被动处理不同，ANC利用声学驱动器（扬声器）来抵消不需要的声场。在考虑对声音进行有源抑制时，有两种主要的控制拓扑结构，即前馈和反馈。前者要求在产生控制信号之前已知干扰情况，它对于周期性或随机性信号是理想的。另一方面，反馈配置可改变封闭声场的动力学以增加阻尼，并且不需要事先了解干扰情况。一种用于结构的被称为正位置反馈（PPF）的改进型反馈可应用于声学系统。在先前的一项研究中，Bisnette和Vipperman（2004年）在PPF配置中使用了一个仿照亥姆霍兹共鸣器建模的调谐共振滤波器来抑制噪声水平。然而，扬声器动力学的存在需要进一步的相位补偿，这可通过一个全通滤波器来实现。此处所介绍的工作通过使用一个高阶补偿器进一步发展了这种控制方法。在本研究中，带通滤波器通过限制相邻模式的相位相互作用来改善多模态控制。通过以电子方式实现控制系统进行了进一步的改进，这使得能够调整控制器参数。在此，提出了一种可调整共振控制器增益的算法。实验结果表明，在没有能量溢出到下一个相邻的未控制模式的情况下，噪声有适度的降低。