My dog often howled and barked when people in the room were laughing. We never did figure out why. I suppose he was trying to laugh along, but I always imagined him scolding us ("Hey! No fun allowed in my house!!! "), so it just made us laugh more and created a vicious cycle.
Maybe she can teach the dogs a "quiet" command? Here's the technique I've heard:
1) Fill a spray bottle with water
2) When the dog barks and you want him to be quiet, say the command and spray his face at the same time.
3) The dog will stop barking long enough to lick the water. Reward him somehow, before he starts barking again.
4) Over time, the dog should associate the command with stopping barking.
But it never worked on my dog because he hated being sprayed. (It's not supposed to be a punishment.)