Abstract: The equivalent theory was used to analyze the flexural vibration of the nickel steel plate and the aluminum honeycomb sandwich plate. Experimental research proves that the lowest eigen frequency of the plate is proportional to the start transmitting frequency of transducers, and the modal density of the plate is proportional to the bandwidth of transducers. A ultrasonic transducer has been designed with an aluminum sandwich plate: under the 5 V signal, the start transmitting frequency is 15kHz, the bandwidth is 15~45 kHz, the sound pressure level is 95 dB，and the fluctuation of SPL is less than  5dB. However, the transducer is thin, the thickness is less than 2mm, the transmitting area is less than 500 mm2, and the transmitting sound signal is omnidirectional.  

Key words: thin panel transducers; aluminum honeycomb sandwich plate; eigen frequency; modal density; flexural vibration