Design and characterization of a PVDF ultrasonic acoustic transducer applied in audio beam loudspeaker

Two different ultrasonic transducers have been designed and fabricated to make a high-directivity sound in air application. Two corresponding methods were used in the transducer structure design respectively, one was based on the circular poly vinylidene fluoride (PVDF) film, and the other was based on the hemi-cylindrical PVDF membrane. The experimental investigations using /spl pi//spl times/70/sup 2/mm/sup 2/ and 120/spl times/6mm/sup 2/ transducers were presented. The resonance frequency and the directivity performance of the transducers were observed. It was found that the resonance frequency of the 120/spl times/6mm/sup 2/ hemi-cylindrical PVDF transducer was consistent with the theoretical calculated resonance frequency. It can be seen that the semi-cylinder transducer was practically possible to the transducer fabrication and can produce an audible sound transmitting in a limited angle range. It showed that the hemi-cylinder ultrasonic transducer had the capability for focusing the sound in a fixed direction in air.