Bark collars operate using sound.

Your dog barks, the collar barks back.

Your dog does not like this and shuts up.

Using bark collars is not the same as your shouting "shut up", which your dog interprets as you joining in the dog barking.

Instead it is an ultrasound noise.

The adjustable strap is 29.5 inch, and the bark collars take 1 x 9v battery (not included)