PVDF cylindrical film air ultrasonic transducer influenced by axial film length

This paper presents a theory of coupling between radial and axial length modes of a PVDF cylindrical film air transducer. The main operational mode is by radial vibration (65 kHz breathing mode) and it is found the axial length vitally influences the device performance and axial length exceeding a critical value does not enhance acoustic output, and power efficiency becomes lower. Experimental data agrees with the theoretical results.