Filled rubber materials system: Application to echo absorption in waterfilled tanks

Abstract

This paper describes a materials system for forming rubber composites with selectable acoustic properties.It is particularly suitable for laboratory use in molding small articles with longitudinal sound speeds and impedances less than (or not much greater than) those of water, and with sound absorption coefficients which may be varied over a wide range. The composites are formed using a common silicone rubber resin (RTV-602) to which various fillers may be added in controlled amounts. In this study, we measured the sound speed, density, and attenuation coefficient for more than 100 samples containing various concentrations and types of these fillers. These data were then reduced to determine the best-fit coefficients in a set of descriptive equations. Thereafter these equations could be used to calculate the filler concentrations needed to form composites with specific required properties. To demonstrate the usefulness and predictability of these materials in an application of general interest, these composites are used to construct several broadband anechoic coatings which reduce tank wall reflections by 20-35 dB at frequencies from 400 kHz to greater than 7 MHz. One-and two-layer coatings were designed using equations derived from Brekhovskikh's treatment of sound propagation in multilayer media. These coatings were then molded as tiles, and their actual performance is compared with that theoretically predicted. When applied to the inside walls of ultrasonic testing tanks, these tiles significantly reduce the tank size needed for various laboratory and biomedical applications. PACS numbers: 43.20.Fn, 43.20.Tb, 81.20.Ti, 43.55.Ev

Effects of Filler Characteristics on the Acoustic Absorption of EPDM-based Highly Filled Particulate Composite

“…Jarzynski [1] first provided an introductory tutorial on the basic nature of sound propagation, the equations governing sound interaction with material properties, and insight into the nature of attenuation mechanisms. Corsaro et al [2] continued Jarzynski's discussion and illustrated the use of his formulation in the development of several sound absorbers of classical design for underwater applications. Madigosky et al [3,4] then described a vital feature of all highly absorbing material systems -the essential presence of voids.…”

Acoustic Coatings for Water-Filled Tanks

“…Examples include the "Wallgone" series of two and three layer coatings, which were based on the material system reported elsewhere (7). Although no longer commercially available, these coatings are mentioned here because their production is sufficiently documented that they have been successfully reproduced by various users, and they remain the most suitable coating available for applications at frequencies near 1 MHz.…”

Design of Piezoelectric Acoustic Transducers for Underwater Applications

“…Instead of simply arranging an array with identical transducers, an array was formed by combining a transducer for transmitting specialization and a transducer for receiving specialization. Based on these transmission and reception arrays, echo control and coating techniques that are less easily captured by the movement of external objects have also been studied [ 16 , 17 ]. Exposure to external moving objects can be reduced through echo control [ 17 , 18 ].…”