Ultrasonic repellers are devices designed to deter pests such as rodents and insects using high-frequency sound waves. These sound waves are typically above the range of human hearing, making them inaudible to people but uncomfortable for many animals. The idea is that the unpleasant sound will encourage pests to leave the area. These devices are often marketed as a humane alternative to traps and poisons. They are easy to use, usually requiring just a power source to operate. However, the effectiveness of ultrasonic repellers can vary, and they may not work for all types of pests or in every environment.