Rats' audible frequencies start at about 200 Hz at the bottom and go up to about 60 Hz from 20 Khz in the ultrasonic range.

This application generates frequencies specialising in the ultrasonic region and displays the waveform on the screen.

10 patterns of multiple frequency combinations
1500hz - 35000hz
15500hz - 35500hz
20000hz - 40000hz
20500hz - 40500hz
25000hz - 45000hz
25500hz - 45500hz
30000hz - 60000hz
30500hz - 60500hz
35000hz - 65000hz
35500hz - 65500hz

Notes.
Depending on the nature of the device speaker, sounds derived from high frequencies may be emitted.
Do not listen to high-frequency sounds with your ear directly over the device speaker for long periods of time as this may be harmful to your health.