Development of a PVDF membrane hydrophone for use in air-coupled ultrasonic transducer calibration

This paper describes the development of a polyvinylidene fluoride membrane hydrophone for application in air coupled transducer calibration. A fundamental analysis is used to demonstrate the suitability of PVDF as a material for wideband hydrophones operating in air. Since calibration of the hydrophone is implemented by employing a laboratory standard device which has been calibrated to a primary standard in water, justification for its use in air is also substantiated by the theory. Validation of theoretical approximations and subsequent experimental results are performed utilising a thickness mode model which is shown to facilitate evaluation of hydrophone operation under a range of imposed boundary conditions. The generation of Lamb waves at critical angles and their influence on the directivity response of membrane hydrophones operating in air is also addressed.