ASA 126th Meeting Denver 1993 October 4-8

5aSA10. Wave vector measurements of empirical design transfer functions.

Joseph A. Clark Michael A. Sartori

Carderock Div., Naval Surface Warfare Ctr., Bethesda, MD 20084-5000

Empirical design transfer functions can be used to predict the radiated noise generated from various components in a system. The Darby method is one example of an approach used to find these empirical design transfer functions. For an immersed and radiating structure, near-field measurements of the pressure field can be wave vector filtered to find the empirical design transfer function from the structural input point to the acoustic far field. Assuming a cylindrical body excited by a force and radiating, a discrete line array of pressure sensing devices are used to measure the near-field pressure. The acoustic pressure data measured at each point are sampled, digitized, time averaged, and frequency transformed. The position-frequency domain pressure is then transformed into the wave vector domain, and the far-field radiation is predicted. The empirical design transfer function is found by dividing the predicted far-field radiation by the input force. The mathematical development of this approach is presented. Simulations are presented for various radiation sources, including a monopole and a discrete line source. The pressure predictions of the wave vector are compared with the pressure directly computed for the sources. [Work supported by ONR.]