Stable sound output is paramountIf the human ear could hear it, it wouldn't be an ultrasound. If you don't hear the whistle, how can you be sure the whistle is working? And the ultrasonic whistle is not suitable for all dogs. Some dogs don't even blink their eyelids when they hear the so-called ultrasonic waves. Have Fun With Your Dog OutdoorsEliminate complex tone settings and make sure every dog can hear the whistle. Great for reminding dog or preventing dog from lacking behavior. Fun to stop dog barking by yourselfWouldn't it be fun if you made your dog stop barking by training it yourself? If the dog barks constantly, try establishing a stop command with the whistle and give the dog a command when training the dog. Reward the dog if he stops all movement and pant. Patience is the real bond between you and your dogSome dogs can be extremely uncomfortable with ultrasound. The principle of ultrasound to stop dog barking is to use ultrasound to make dogs feel uncomfortable. A can of compressed air for dogs/anti bark for dogs would do better, but can you be so cruel to dogs? Two-in-one designThe whistle is used to issue commands and the clicker is used to give the dog an affirmation after completing the command.