Gracie Ruth is our Early Warning System.

She has the most amazing hearing, and makes sure everyone knows when she perceives danger. G's definition of danger: any noise or movement, real or imagined that she hears or sees.

Penny's in a can won't work for us because Boo is hypersensitive to such noises and gets uncontrollably afraid. So I do a sort of Dog Whisperer type of thing. I started out turning her away from where she was focused and telling her Quit, No, shhhhh. As soon as she'd pause I'd praise her. Of course she'd start right back up with her next breath, and we'd go through it all again. Then it got so that I just had to tug gently on her beard and say Quit, shhh. Moved on to just a touch on the back of the neck and the command. Now it's rare that I have to touch her, I simply just say shhh and she'll just yammer. You know the sound, where they aren't barking but making a yammer-yammer-yammering sound, kind of under her breath. I always thank her for letting me know she kept us safe from certain death or horrible mutilation and that usually satisfies her.
The other thing is that when they run outside to bark at things. Boo runs out first barking and sound all big and tough, G is hot on his heals...barking and poking Boo...and now Yogi is hot on G's heals barking and poking her. It's hysterical to see the little Yorkie Train heading out to conquer evil and keep their home safe from all attacks. Homeland Security should have such dedicated workers.