These are the four types of bark collars

Spray bark collar: These collars will release an unpleasant plant-based scent around your dog’s nose. Most spray collars use citronella, which is a natural repellent. While we may enjoy this smell, bugs and animals do not.
Ultrasonic bark collar: A dog’s hearing is far more sensitive than ours, making them able to hear pitches and frequencies that we can not. Ultrasonic bark collars, when triggered, will produce an “annoying” high-pitched sound that only dogs can hear.
Vibration bark collar: A vibration collar, when triggered by your dog’s bark, will activate a series of vibration intensities in your dog’s collar. These are more of an annoyance to the dog, and if used properly, the dog will associate the vibration as a result of the bark.
Static shock collar: First and foremost, it should be noted that Dr. Houpt advises against the use of a shock collar. When your dog barks, a static shock will be administered through electrodes on the dog’s collar. These shocks are similar to what we feel when we get shocked by static electricity. Many collars offer various settings and intensities depending on the dog’s size and severity of the barking.

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