Ultrasonic bark deterrents are devices designed to reduce excessive barking in dogs. They emit a high-frequency sound that is unpleasant to dogs but generally inaudible to humans. When a dog barks, the device is triggered, releasing the sound to discourage the behavior. These deterrents can be used indoors or outdoors and are often portable. They are considered a humane alternative to other training methods, as they do not involve physical punishment. However, effectiveness can vary depending on the dog's temperament and the environment in which the device is used.