Abstract
ABSTRACT
According to the importance of Active Noise Control (ANC) in 3D spaces such as vehicle cabins for reducing unwanted noises inside cabins, the purpose of this paper is to demonstrate the finite element (FE) modeling, simulation and analysis of an ANC in a 3D acoustic passenger car cabin with filtered-X LMS adaptive feed forward controller. For this purpose, after creating an acoustic FE model of the passenger car cabin and calculating its resonance frequencies and mode shapes; several transfer functions of primary, secondary and feedback paths of the acoustic field is estimated in digital domain in accordance with frequency responses obtained from FE model in order to simulate the behavior of ANC system. In all simulations, acoustic feedback effect is considered and the acoustic feedback neutralization technique is used to reduce or overcome the instability potential of this effect. The performance of different configurations of multi-channel "FXLMS" ANC systems is studied with "off-line" modeling technique using Finite Impulse Response (FIR) filters. The obtained results are useful for optimal placement of secondary sources and error microphones. It is found that, the acoustic pressure attenuation inside cabin can be significantly reduced if the control source is placed in close proximity to the reference microphone. However, increasing the number of sensors and/or the number of control sources located remotely from the primary source, have little impact on the maximum achievable reduction in the acoustic pressure in the cavity.