Advanced Ultrasonic Dog Bark Stopper Control Can be highly effective in controlling nuisance barking - your own dog or your neighbour's dog. The unit senses the noise of barking dogs. When activated the device releases a very loud ultrasonic noise, this noise is at a too high a frequency for most humans to hear but is alarming and uncomfortable to dogs. The dog will learn to associate this noise with the barking and in most circumstances the barking will desist or be greatly reduced. For most dogs, they are sensitive to frequency around 23kHz and the device emits fixed frequency of 22kHz to 25kHz.