I've never used the whistle so I don't know how well it would work. With Ruby and Reno I've used the water bottle method and it has been very effective in stopping unwanted barking. In fact now, I don't usually have to even spray them, just make the "uh-huh" noise and they stop barking. It took only a couple of times spraying too, before they learned.
__________________  ~Ruby, Reno, Razz, & Jack~ |