Global feedforward active noise control in vibro-acoustic cavities without increasing structural vibrations.

Abstract

Interior noise in vibro-acoustic cavities may be generated due to acoustic and structural disturbances. Earlier studies have shown that for global control, the maximum reduction in acoustic potential energy can be realised by using an optimum combination of acoustic and structural actuators. However, it is observed that this reduction in interior noise may also be accompanied with an increase in kinetic energy of the cavity structure. This paper presents the development of a feedforward technique for active noise control in vibro-acoustic cavities ensuring that the noise reduction does not lead to an increase in kinetic energy. The problem is formulated as a constrained minimisation problem to minimise the acoustic potential energy subject to a constraint that the kinetic energy does not increase. Through a numerical study, it is shown that the optimum solution of the above problem indeed is favourable in terms of reduction in acoustic potential energy in the cavity and kinetic energy of the structure. The paper further proposes a method for solution of this constrained minimisation problem using a penalty function method and solution of sequential unconstrained problems. The proposed method is validated through a numerical study on a car-like cavity for single- and multi-tonal noise.