Acoustic Radiation from Line- and Point-Loaded Plates: Uniformly Asymptotic Solutions.

Abstract : The theoretical analysis for predicting the acoustic radiation from an infinite fluid-loaded elastic plate excited by a line or a point force is presented. The acoustic pressure radiated by this coupled plate-fluid system is obtained by the use of the Fourier transform method for line force excitation and a Hankel transform for point force excitation. The integral representation of the radiated acoustic pressure is evaluated by three methods based on the steepest descent path (SDP). The first is the widely used saddle point method which can only lead to the farfield solution, The first-order approximation due to the contribution at the saddle point is obtained with the assumption that all the poles of the integrand are located far away from the saddle point and SDP. However the leaky wave pole may approach the saddle point when the frequency is above the coincidence frequency. Thus the saddle point method is modified such that all the singularities of the integrand are explicitly isolated regardless of their proximity to the saddle point. Keywords: Acoustic pressure, Asymptotic series, Saddle point method, Structural damping, Fluid loaded plate, Timoshenko Mindlin theory.