ASA 125th Meeting Ottawa 1993 May

2pEA11. Comparisons of two encapsulating methods on the acoustic performance of a passive cylindrical array.

Alan K. Walden

Thomas R. Howarth

Mark L. Pecoraro

Allan C. Tims

Naval Res. Lab., Underwater Sound Reference Detachment, Orlando, FL 32856

The purpose of this study was to determine the effects of encapsulation methods on the acoustic performance of a passive, cylindrical, high gain, broadband (multi-octave) array. Both an oil-filled boot and a polyurethane coating were considered. The array consisted of 36 lead titanate elements mounted in a 3 by 12 matrix along 180 deg of the circumference of a steel cylinder. Original intentions were to rely on the oil-filled booting to ensure performance void of transverse mode coupling between neighboring elements. Measurements of the oil-filled array showed a ``scalloping'' effect in the radiation patterns as well as significant disturbances throughout the receiving response [Howarth et al., J. Acoust. Soc. Am. 91, 2325--2326 (A) (1992)]. This study took the same array and encapsulated it in a polyurethane elastomer. Experimental data indicate that many of the perturbations notes in the oil-filled configuration were considerably diminished after potting. Performance comparisons between the two encapsulating methods shall be presented and discussed. [Work supported by NSWS/Carderock Division.]