ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

4pNSb6. Parametric coating.

Vladimir V. Arabadzhi

Inst. of Appl. Phys., Russian Acad. of Sci., Dept. of Hydrophys. and Hydroacoust., 603600 Nizhny Novgorod, Russia

A control algorithm for the multilayer parametric coating is suggested. The frequency of layer parameter manipulations is much larger than the incident wave frequency and the total multilayer coating thickness is much less than the incident wavelength. This denotes the space-time locality of the damping system. The coating provides the boundary conditions of the acoustical blackbody at low frequencies for a surface of arbitrary form and wave dimensions. This case includes the incident waves absorption and the forward scattering without backward scattering. The algorithm does not require wave field measurements. It assigns the law of coating parameters to time changes only (instantaneously on the whole surface). Algorithm realization may be based on the electrorheological liquids which make fast transformations from the liquid state to the solid one and back due to the applied electric voltage at all usual temperatures. The results of numerical simulation are presented.