Design of a hydrophone array for littoral waters

Summary form only given. This presentation documents the engineering effort, fabrication, and subsequent calibration results of a line array, USRD type F81, currently used by the U.S. Navy to collect acoustic data in littoral waters. Littoral waters present a complicated acoustic environment, but measurement difficulties can be minimized by using a transducer or array configuration designed for the specific application. The hydrophone array type F81 was designed and fabricated to assist in studying the impact that ocean biological life has on submarine sonar. Relevant engineering equations used to predict performance for transducers and arrays are the main focus and discussed in some detail, but application is also discussed. The engineering discussion includes the parameters; Free Field Voltage Sensitivity (FFVS), directional response, array capacitance, effects of cable capacitance, wiring sensors in a parallel/series combination, and sensor spacing. Additionally, selection of sensor material, the acoustic window material, and unique mechanical configurations used for fabrication are examined. Issues of reliability for underwater transducer designers are implicit throughout this presentation. The F81's low weight, flexibility, and strength help facilitate easy deployment and retrieval from nearly any research vessel of opportunity. The F81 transducer has been in service for about three years and, to date, successfully employed by the Naval Research Laboratory.