1pPA1. Experimental results for transmission of a finite-amplitude, focused sound beam at a curved interface between two media.

Session: Monday Afternoon, December 2

Time: 2:00

Author: Inder Raj S. Makin
Location: Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98105
Author: E. Carr Everbach
Location: Swarthmore College, Swarthmore, PA 19081-1397
Author: Mark F. Hamilton
Location: Univ. of Texas, Austin, TX 78712-1063


Transmission of an intense focused sound beam through two different liquids separated by a curved interface was investigated experimentally. The acoustic field was generated by a 2.25-MHz tone burst from a focused source of radius 19 mm and focal length 159 mm. Measurements of propagation curves and beam patterns were made using a PVDF needle hydrophone. The source was placed in water, the first liquid, and either lamp oil (c[inf water]/c[inf oil]=1.08) or a 50% glycerin--water mixture (c[inf water]/c[inf mixture]=0.85) was used as the second liquid. Curvature at the interface between the water and the second liquid was controlled by using a thin ((approximately equal to)40 (mu)m) polyether polyurethane membrane. Both concave or convex curvatures, with radii varying from 90 mm to infinity (plane interface), were achieved by varying the hydrostatic pressure between the two liquid chambers. Measurements were compared with theory, presented earlier [Makin, J. Acoust. Soc. Am. 95, 2864(A) (1994)], based on the nonlinear parabolic (KZK) wave equation. Reasonably good comparison between theory and experiment was observed for the first four harmonics generated in the incident and transmitted fields for interfaces with various curvatures, and located in either the pre-focal or post-focal regions. [Work supported by NSF.]

ASA 132nd meeting - Hawaii, December 1996