Easy Training Dog Whistle - Use the whistle to stop barking instead keep yelling pet’s name, ultrasonic sound training tool to teach your dog unlimited commands such as recall, sit, come, stop,baring, stay, and toilet training. Adjustable Frequency Whistle - Aptoyu dog whistle can be adjustable to multiple frequencies which easily train your dog unlimited commands, rotate the adjustable nut to find a suitable pitch frequency for your dog. Safe Dog Whistle - Use Silent Bark Control for dogs stopping useless barking, although ultrasonic sound isn’t “loud”, it’s loud enough for dogs to hear, it’s easy to catch dogs’ attention by blow the whistle, will not hurt your dogs ears.