Acme's Silent Dog Whistle made in England since 1935 is the perfect dog training whistle  for town or country close or distance work. It offers an adjustable frequency range from 5400  Hz to 12800 Hz that can be tuned to your dog's hearing making it the most effective way for  trainers to communicate with their dogs. Made of lightweight durable stainless steel the  whistle's sound is barely audible by humans but can be heard by dogs over great distances.  The excellent design of this whistle includes a handy cap attached by a lightweight chain.