Sound radiation from a vibrating body in motion

Abstract

Past studies of acoustic radiation problems have been concerned with sound waves generated by either a vibrating body or a moving point source with no dimensions of its own. This paper presents a method for determining the acoustic field radiated from an arbitrary object undergoing, simultaneously, a harmonic oscillation and a spatial motion with respect to the surrounding fluid medium. At this stage of the investigation, the turbulence and flow distortion caused by the motion of the vibrating body are neglected. The method is based on the assumption that the surface of the vibrating body can be described in terms of a distribution of simple monopole and dipole sources. Utilizing a linear coordinate transformation, one is then able to reduce the problem to that of radiation from a stationary source for which the analytical solution has been obtained [Morse and Ingard, Theoretical Acoustics (Princeton U.P., Princeton, NJ, 1986)]. The total acoustic field is the sum of contributions from all the simple sources on the surface of the moving object. The method is illustrated using a vibrating sphere moving with either constant or time‐dependent velocity profiles relative to the surrounding medium. Extension of this method to impulsive motions is discussed. [Work supported by NSF and WSU Institute for Manufacturing Research.]