What is the most effective shock collar for a loud dog?

There is no scientific evidence to support the claim that shock collars are an effective solution for loud barking. Research consistently indicates positive reinforcement and behavior modification, not aversion methods based on physical or psychological punishment such as collars that spray citronella, emit ultrasonic noises, or even apply small amounts of electric current, are significantly more effective. In many ways, the use of aversion-based products and the belief that they produce the best training outcomes is one of the most unfortunate myths still pervading modern pet care culture.