I'll state the obvious but with no intent to poke fun at anyone.
You will need speakers and mics capable of performing between 20 kHz and 100 kHz.
It seems that the term speaker applies to audible energy as does the term microphone. In my very limited experience the device that generates converts the electrical "ultrasonic" energy is called a transducer. There is probably nothing wrong will calling it a speaker but by adjusting the terminology you might search and find more information.
Worth noting - while the normal use for speakers and mics is within the normal range of hearing it's clear that many of these do perform above 20 kHz - possibly not the most efficiently but they do work. You'd have to check the specifications or for items on hand, try it and see.
I have read that the impedance of a "speaker" changes with frequency, among other things. Make sure you understand where your speaker is at if you push it beyond the normal range.