Ultrasonic rat repellent is an electronic transmitter of high-frequency sound well above the 20 kHz frequency which is the upper limit of the hearing range of the human ear. It emits intensive sound at high decibel levels (sound pressure) that is audible and painful to rats and mice but is inaudible and harmless to humans. The rats & mice will usually leave the area being protected by the ultrasound. They do not get killed. It is a stand-alone system with an additional transducer.

Once the device detects the presence of a bird, bat, pest, rat, monkey, and many more it emits high-frequency sound waves like predator calls or naturally recorded animal distress signals that frighten away animals. The devices typically get plugged into an electrical outlet.