2pSA8. Application of near-field holograms that contain noise to predict the far-field scattered pressure of a finite cylinder with spherical endcaps.

Session: Tuesday Afternoon, December 3

Time: 4:40

Author: Ronald G. Hughes
Location: Vector Res. Corp., 2101 E. Jefferson St., Rockville, MD 20852
Author: Gerard P. Carroll
Location: Naval Surface Warfare Ctr., Carderock Div., Bethesda, MD 20084-5000


Near-field acoustic holography has been used in several studies to understand the radiation characteristics of various submerged objects. Further, the process has also been used to a lesser extent to examine acoustic scattering. Near-field holograms in either radiation or scattering studies are degraded by errors associated with background noise and sensor placements. In addition to these sources of error, the application of near-field holography to characterize the scattered field are further degraded by the requirement to remove the incident field from the scattered field. The significance of placement errors, background noise, and the removal of the incident field from the scattered field are presented for the case of a cylinder with spherical endcaps. The velocity and pressure distributions on the cylinder surface were calculated using SARA 2D and the pressure field was calculated using a Helmholtz integral method. Quantitative predictions of the degradation of the far-field pressure for a cylinder with spherical endcaps based upon reconstructions from near-field hologram planes that include various types of errors will be presented. [Work supported by ONR.]

ASA 132nd meeting - Hawaii, December 1996