Ultrasonic devices do nothing to repel or kill pests such as mosquitoes, according to the University of Florida's Institute of Food and Agricultural Sciences. The devices do not help to protect humans or animals from diseases carried by the pests.
None of the claims made by ultrasonic pest repellent devices have been scientifically proven. There is no evidence to support the claims made by the device's manufacturers, as the U.S. Federal Trade Commission states. In fact, the FTC has charged a manufacturer with making unsubstantiated and false claims while selling the ultrasonic products. In most cases, old-fashioned repellents and prevention are the best ways to combat pests.