Automated digital benchtop calibration system for hydrophone arrays

A calibration system is described which can measure the complex sensitivity and directivity patterns of hydrophone arrays, such as sonobuoy arrays, in which the hydrophone elements are individually accessible. These arrays are often deployed over a great distance in the ocean. Calibrating them under free-field conditions would be an extremely difficult task. The system described here allows for their calibration on a benchtop. The entire calibration system is controlled by a computer and requires minimal operator intervention. The computer algorithm is also applicable to hydrophone arrays which do not have individually accessible elements. Results are presented which compare measured directivity patterns with theoretical directivity patterns calculated from the measured complex sensitivities of the individual array elements.