More pictures would help a lot here. Top, bottom, sides, etc., as well
as a shot with something else in the picture like a ruler so we can get
an idea what the size is.
Wow... To know it's resonant frequency, you have to sweep it witha function generator (sinewave) connected to it across a 600 ohm resistor and observe the waveform with a scope connected directly to the transducer. Please respect the natural use of the transducer (If it's an underwater transducer, put the output port under water).
While sweeping it, you'll notice variations in the sinewave's amplitude. The resonant frequency will be the frequency at which the amplitude will be the LOWEST. (lowest impedance).
thanks for help !
i will tell you about my process
i was repair some ultrasonic clearning and it 's working good .but some machine i can't repair because some component is not found so i want made a new board