The only other alternative to a bark collar is an ultrasound system, which emits frequencies that are inaudible to humans, but very annoying to dogs. These devices are similar to bark collars, in terms of how the operate, as they are also activated every time they detect a loud noise. However, they are not equally effective at training your dog, or actually stopping it from barking at all.
You could try a canine behavior specialist, or even a veterinarian could know some successful methods to get your dog to stop barking constantly and unnecessarily. Most importantly, never act violently towards your dog, because they are living beings that suffer just like humans do. Positive reinforcement is always the best approach to training your dog.