Acoustic transducer calibration system

Multibeam sonars are being used increasingly to image fish. To realize their quantitative potential for measuring the numerical density of fish and other aquatic organisms, it is essential that they be calibrated. This can be done by the use of standard targets. The calibration of narrow beam acoustic arrays requires precise angular control of the transducer under test. Precision is defined as 0.1/spl deg/. This degree of control is achievable with a precision rotary table typically used in the CNC machining industry. This paper describes the system specifications and the development of the LabView interface that coordinates position and acoustic data acquisition. The initial evaluation of the rotary table for repeatability and possible backlash demonstrated that the system was within the required specifications. Finally, representative acoustic measurements made with a Kongsberg-Simrad SM 2000 and Reson SeaBat 8101 multi-beam sonars using the new system are presented.