Application of NAH method for the prediction of sound radiation from a flexible box structure

Prediction of noise radiation from the thin flexible structures, which encloses sound sources is important for the structural design to develop a quieter product. There are different direct and indirect techniques are existing to know the sound radiation of the machine or structure. The direct method such as sound intensity method and indirect methods or inverse techniques includes Near-field Acoustic Holography (NAH) and beam forming. NAH is one of the good inverse techniques to predict the vibro-acoustic properties of the sound source. In this method, acoustic quantities can be reconstructed on the surface of a vibrating structure based on sound pressure measurements made at a set of points in the near-field of the source. These NAH methods are the ill-posed inverse problems due to the existence of strongly decaying, evanescent like waves. Regularization is used to overcome the ill-posed problem. The purpose of this investigation is to predict the sound radiation characteristics of a box structure with one flexible wall. The acoustic quantities are reconstructed with NAH technique.