Active control of radiated sound using near field pressure sensing

How to pick up error information is a key step in the design of an adaptive acoustic structure. In this paper, a near-field sound pressure sensing approach is proposed to implement active control strategies. The idea is that a near-field squared pressure after active control is used as error signals and transformed into an objective function in adaptive active control process. Firstly formulae for calculating near-field pressure radiated from a flexible structure are given, then three objective functions are deduced and compared, taking into accounting active control of radiated single and broadband noise. Finally influences of constraint conditions on noise reduction are discussed in detail. It is concluded that from analytical expressions and numerical examples that radiated sound power of a finite of pressure radiation modes and near-field squared pressures can be used to construct the objective function applied to the adaptive acoustic structure.