Tank coatings for ultrasonic echo reduction

Abstract

A filled‐rubber materials system with selectable and continuously variable acoustic properties is described and used to form broadband anechoic tiles. By applying these tiles to the inside walls of acoustic testing tanks, wall reflections are reduced by 20 to 35 dB at frequencies from 0.5 to 10 MHz. This is advantageous since it allows the use of smaller examination tanks, for example in ultrasonic testing and biomedical applications, and permits the use of cw tanks of tractable size, for example in schlieren and acoustic‐visualization studies. The tank coatings developed include one and two layer tiles, 0.15 to 0.65 cm thick. Using a theoretical model of sound propagation in multilayer media, we first calculated the optimum material properties needed to construct tiles meeting specific echo reduction requirements. These materia] requirements were then met by choosing the type and concentration of fillers added to an RTV‐602 silicone rubber base. The subsequently measured performance of these tiles agree with that initially predicted by theory.