Hooking up an ultrasonic transducer?

[gsjbjt]

Hello,
Sorry if this seems like a very basic question to experienced engineers, but I'm a beginner in this area just looking to learn---
I thought up a research project, one of the components in which I need to generate ultrasonic waves. There were scrapped ultrasonic ring transducers (look like these: http://i01.i.aliimg.com/wsphoto/v1/585168415_1/-font-b-Piezoelectric-b-font-font-b-Transducer-b-font-for-font-b-ultrasonic-b.jpg) lying around from someone else's previous research project, supposedly from a sonoluminescence kit. Currently I have a wave function generator and an oscilloscope on hand.
I'm not exactly sure how to go about doing this --Is generating ultrasonic waves as simple as connecting two wires from each transducer to the wave generator?
How is it possible to test/detect whether waves are actually being generated (if I understand correctly, there's no distinguishable sound or vibration)?
Is it possible to adjust the frequency of the waves that the transducer produces by adjusting the settings on the wave generator, or is the wave frequency a set, physical property of the transducer?

I would really appreciate it if anyone could clear up any misunderstandings I have, as well as clarify the process for using these transducers.
Thanks in advance!

 

[NascentOxygen]

I think if you dip the transducer into water it should throw up some spray. The maximum output will be at the transducer's resonant frequency.