ASA 124th Meeting New Orleans 1992 October

5aSA1. Sound radiation from a fluid-loaded finite cylinder as a function of spacing between forcing pulses.

J. Adin Mann, III

Daniel H. Kruger

Dept. of Aerosp. Eng. and Eng. Mech., 2019 Black Eng. Bldg., Iowa State Univ., Ames, IA 50011

Sound radiation from a spherically endcapped, point-driven, fluid-loaded, cylindrical shell will be presented in the time domain. The impulse response functions that are measured with near-field acoustical holography are used to simulate the response to a synthetic driving force with two pulses. The individual signals are Gaussian-windowed single-frequency pulses. As the time spacing between pulses changes, the amount of energy radiated by the shell varies greatly---from less than to greater than the energy radiated by a single pulse. These variations are explained with a frequency domain model and by the average energy radiated from different points on the shell. One can dissipate the mechanical energy input to the shell by the force driver either through sound radiation or by damping in the shell. Thus these results show that it is possible to force more energy to be damped in the shell and to reduce the amount of sound energy radiated to the far field. These observations cannot be made when analysis is confined to the frequency domain.