Laser-Assisted Prediction of Acoustic Radiation and Scattering

Wayne State University, Detroit MI

Investigators

Abstract

Sean F. Wu, P.I. Wayne State University NSF Proposal No. 0084723 Laser-Assisted Prediction of Acoustic Radiation and Scattering Project Abstract This research aims at developing a highly accurate and efficient methodology for predicting acoustic radiation and scattering from an arbitrary object. A non-invasive three-dimensional laser Doppler velocimetry (LDV) is used to scan and measure velocity vectors of suspended particles in an insonified fluid medium over a control surface that completely encloses the structure under consideration. The measured velocity vectors are taken as input to an explicit integral formulation to calculate the acoustic pressure field. This methodology is superior in that: (1) it correlates the field acoustic pressure directly to the particle velocity distribution; (2) it provides unique solutions for acoustic pressures in all frequencies; and (3) it enables one to solve transient acoustic radiation problems conveniently. Applications of this new technology can be found in predicting sound radiation and scattering from any structure. In particular, it is suitable for a flexible or lightweight structure, or for a structure that does not allow for conventional contact measurement devices. This project is carried out jointly between Mechanical Engineering Department and Electrical & Computer Engineering Department of Wayne State University. This joint research has a far-reaching impact on computational acoustics. It is expected to revolutionize the current way of calculating acoustic radiation and scattering from an arbitrary object, and significantly improve the efficiency in numerical computations. This is especially true for a complex structure for which the fluid-loading effect must be considered. Applications of this new technology can be found in the analyses of the sound field generated by an underwater or ground vehicle. Using this new method, engineers can assess the performance of noise transmission into an aircraft cabin or vehicle passenger compartment, or vehicle pass-by noise levels. The knowledge thus gained will enable them to tackle aircraft and vehicle vibration and noise problems in a cost-effective manner.