High frequency ultrasonic dog training whistle can produce tubular sounds that can be heard by the human ear, as well as ultrasonic waves that cannot be heard by the human ear.The emitted ultra long sound waves can be heard by pets from a few kilometers away, but at this time, human ears cannot hear them.It has sound wave adjustment screws and can adjust the frequency freely, making it easy to operate. The stainless steel material is durable, and the ultrasonic wave propagation energy is large, which can propagate long distances in a straight line. This product is a good helper to help you communicate with your pet.