Visualization of Sound Radiation From a Bowling Ball

Abstract

Abstract This paper presents results of an investigation on visualization of sound radiation from a bowling ball via the Helmholtz Equation Least Squares (HELS) method [Wang and Wu, 1997; Wu and Wang, 1998; Wu and Yu, 1998]. In conducting the tests, the bowling ball was excited by a vibration shaker using a random signal. The radiated acoustic pressures were measured over both conformal and planer surfaces at certain distances away from the source. The measured data were taken as the input to a computer model based on the HELS formulation. The reconstructed acoustic pressures on the surface and in the field were compared with the measured data at the same locations. Also shown are comparisons of the reconstructed and measured acoustic pressure spectra at various locations on the bowling ball surface. Results demonstrate that the accuracy of reconstruction based on measurements over a conformal surface is much higher than that over a planar surface. This is because a planar surface often extends beyond the near-field region, thus making the accuracy of measurements inconsistent. Nevertheless, satisfactory visualization of acoustic pressure distribution over the entire bowling ball surface can still be obtained, at least in the low-to-mid frequency regime, based on the measurements over a finite, planar surface on one side of the source. Such a capability is unique to the HELS method. However, the efficiency of numerical computations of the HELS method is expected to deteriorate at high frequencies, a difficulty inherent in all expansion theories.