Pet Parade Dog Repeller and Training Aid, Emitting a piercing Ultrasonic dog repellent tone Eliminates barking and annoying behavior by emitting a piercing ultrasonic tone that pets hate But humans can barely hear. Stop dogs from jumping, barking and biting. Protect yourself from dangerous dogs while walking, jogging, or bicycling. Ultrasonic tone is barely audible to humans. Works with any dog. Can also be used to train dogs. Requires 9-volt battery.