I feel for ya. As ARCHIE said, it can rattle your nerves.
We've tried three different strategies. We started with pennies in a can. That worked great for a while. A few months later, it did nothing but make him bark more. So we switched to a water bottle. Worked great for a few months, then it lost its effect. Right now, we're on one of the sonic things that emits a high pitched sound when you hit the button that bothers the dogs' ears. That is now working great.
So if something works for a while and then stops working, it has worked for us to try something else.
.......... kinda like how I have to change shampoos every once in a while or they lose their effect.
