(2 pk.) Dog Training Whistle to Stop Barking - Ultrasonic Sound Repellent - Silence Your Dog Great for Hunting Dogs and Stubborn Dogs Neighbor's Dog won't stop barking? This whistle is an excellent and safe deterrent to silence him/her. No more sleepless nights. This whistle, like all silent whistles, is not completely silent. You will hear it when you use it. All whistles produce a secondary audible sound that is caused by the air that goes across the whistle. Blowing lightly on the whistle reduces the audible sound, and actually increases the ultrasonic sound that your dog hears. Train your dog to follow simple commands such as "sit", "come", "stay", "down" and to change direction by using different whistle patterns for each one. Adjustable Frequencies - By simply turning the screw at the end of the whistle, you can adjust the frequency to find the one that your dog responds to.