Koolatron PC16 Super Bark Free - Dog Training Device Super Bark Free uses an old-age principle of Negative Enforcement using Sound to help train dogs to stop annoyance barking. The Super Bark Free works by emitting an ultrasonic noise every time it senses barking dogs. The Super Bark Free has a specially designed sound selector that lets you choose frequencies which can only be heard by dogs and cats or lower sound tones audible to human ears. This ultrasonic animal control device operates in a seemingly quiet manner to stop barking dogs.- SKU: KLT117