ASA 127th Meeting M.I.T. 1994 June 6-10

3pSAa8. Far-field sound radiation study of a steel beam with a T bar by k-space filtering.

Ruey-Chang Wei

J. Adin Mann, III

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

By using the concept of the radiation circle, simulations were done to investigate the contributions to the far-field radiated sound from different waves in the structure. The far-field radiated sound is from the waves with wave numbers inside of the radiation circle, which include evanescent and propagating waves. The simulations show the important role of the evanescent wave in the sound radiation. K-space filtering involves removing energy in spatial wave numbers that are outside the radiation circle, leaving only the energy that radiates to the acoustic far field. The application of the k-space filter can be used to locate the area of a structure that radiates sound to the far field. The experimental results for the steel beam with a welded T bar shows that the T bar radiates significant sound to the acoustic far field, even though the size of the T bar is small. The k-space filtering is proved to be very useful in the study of sound radiation for a structure with discontinuities or inhomogeneities. [Work supported by ONR, Grant No. N00014-93-1-0493.]