<title>Finite element/boundary element simulation of interior noise control using active-passive control technique</title>

Abstract

ABSTRACT This paper presents a finite element/boundary element (FE/BE) formulation for modeling and analysis of active-passive noisecontrol system. Finite element method is proposed to model the smart plate with surface bonded piezoelectric patches and theenclosing walls and the dual reciprocity boundary element method is proposed for modeling the acoustic cavity. The use ofFE/BE method facilitates us imposing the impedance boundary conditions at the fluid/passive absorber/structure interface.An output feedback optimal controller design procedure is given for the smart plate system with active patches for the lowfrequency regime.KEYWORDS: Finite element/boundary element modeling, cabin noise control, optimal controller 1. INTRODUCTION The primary contributions to the noise spectrum inside a helicopter cabin are the main rotor, tail rotor and turbines, whichoperate at frequencies ranging from 50 to 500 Hz and the gear mechanisms in the main transmission, operate at frequenciesabove 500 Hz [1]. Traditional means for the control of undesired sound and vibration is often referred to passive methodssince no power source is required for the control system. The noise reduction is achieved by either insulating the enclosurewalls or by covering them with porous sound absorbers. These passive control methods are quite effective at high frequenciesor at narrow frequency bands. At low frequencies the active control method using segmented piezoelectric patches is found tobe an attractive alternative to passive methods.For modeling such active vibration and radiated noise control system using embedded or bonded discrete piezoelectricpatches, finite element (FE) method is found to be an efficient and more practical method [2-7]. Modeling and analysis ofthese smart structures using FE method have been studied earlier by researchers in CEEAMt [3-711.