Active noise control for complicated space by concentrated mass model

Abstract

Several adaptive feedforward control methods have been proposed in conventional research on active noise control. In these methods, noise control is achieved by adding in a reverse-phase control sound of the same amplitude to noise near an error microphone. Because this method is aimed at controlling only near the error microphone, the control area is inherently narrow. We propose an alternative method of noise control for an all closed space. The proposed method is based on state feedback control and models the acoustic space by the concentrated-mass model. In this, the acoustic space is modeled as masses, connecting springs, connecting dampers, and base support dampers. Further, a loudspeaker as control source is also modeled as a mass–spring–damper system. In this paper, we show the basic design of a control system for two-dimensional complicated acoustic spaces. The acoustic space are modeled in a concentrated-mass model, and the state feedback control system is realized with pole placement. The number of degrees of freedom is reduced by using modal analysis, which reduces the computation time of the controller. Furthermore, theoretical limit of the control effect are considered on the case where sound sources are arranged asymmetrically in a simplified system. Based on the test results, we design a control system that controls to reduce interference between specific mode groups. The method is applied to complicated closed spaces, and the effectiveness is confirmed by numerical calculation.