What are ultrasonic anti-barking devices?

Ultrasonic anti-barking devices, also known as ultrasonic emitters are specially designed devices that emit an ultrasonic sound that helps control the barking dog. The sound is very high pitched and can only be heard by the dogs and hence is not irritating to the human ear. It is an irritating sound for the dog but it helps them understand when barking is wrong and without purpose. 

The element of surprise associated with the sound helps control the dog and stop barking. The modern ultrasonic anti-barking devices can detect excessive barking and emit sound. If the dog does not cease barking, the sound continues to increase until the dog surrenders.