Yeah people,cats can hear more than 70khz, we humans don't, and the classic devices for register ultrasounds(lets say under water) is called SONAR...other one the machine doctors uses in your pregnant woman baby bump...
But I don't discourage you batman!!!,If your really wanna record those frequencies anyway ,set your sequencer to 192 khz, waste computer resources ,and buy a modern stuff like this one:
http://www.ultrasoundgate.com At least they use ultrasound microphones, for hearing bugs and bats:
Ultrasound Microphones
And obviously, I think they finally use an under-sampling mechanism! , else, you not gonna hear what is recorded, you're human.