I have some 40kHz ultrasonic transducers (the same type as which you find in the common Arduino ultrasonic distance sensors.) All information comparable to a datasheet I got was:
I don't get how to read it or how to calculate the current drawn, which I need to know when making or buying a amplifier. It does show the capacitance at 1kHz. I guess they use that as a worst case scenario or such, however they don't show graphs showing how it behaves at different frequency ranges, at different voltage ranges, and above all it doesn't seem to show units.
Since it is a very commonly used ultrasonic transducer perhaps someone knows how to calculate the maximum current draw at a specific frequency and voltage, and/or a better datasheet or information or a close enough estimation of what current it will draw or what unit the value is in.