Dog Whistle is a free application that helps you to train your dog.
Dog whistles emit sounds in the high frequency range. Humans can only hear up to 20 kHz, but dogs have much better hearing. Since dog whistles are silent to humans, but loud to dogs, they are perfect for training dogs.
This Dog Whistle app can emit high frequency sounds anywhere in the range from 100 to 22,000 Hz.
Remember, just because you can't hear it, doesn't mean your dog can't. Please use this application responsibly.