HAOYI Effective Dog Barking Deterrent: The dog barking device is designed with 4 working levels, effectively using ultrasonic waves to stop barking from 30 feet away, covering both areasindoor and outdoor, but also preventing barking from the neighbour's dog. Safety Anti-Bark Device: The ultrasonic anti-bark device adopts high-pitched ultrasonic technology, which is harmless to pets above the human hearing range, but will attract the attention of pets. dogswithout painful stimulation. Effective for most dogs: The ultrasonic anti-bark device is suitable for most breeds and sizes, but not for deaf or hard of hearing dogs. Some dogs may be afraid or dislike the sound of the ultrasound anddon't stop barking in the first place. Please allow up to 2 weeks of training time.