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 indoor areas and outdoor, but also prevent barking from neighbor's dog. Safety Anti-bark Device: The ultrasonic anti-bark device adopts high-pitched ultrasonic technology, which is harmless to pets above human hearing range, but will attract dogs' attention without painful stimulation. Effective for most dogs: The ultrasonic anti-bark device is suitable for most dogs. breeds and sizes, but not to deaf or hard of hearing dogs. Some dogs may be afraid or dislike the sound of the ultrasound and won't stop barking in the first place. Please allow up to 2 weeks of training time.