Around camp I put a bell on one of my 3 so I can tell where they are. And if something is chasing them I should be able to hear the bell jingling in a different way. I haven't actually had any wild predator problems either. But dogs are another matter. And so are javelinas. Dogs would only be a problem if other people are nearby. But javelinas can show up anytime, anywhere in the lower elevations off my area. They aren't predators, but they have poor eyesight and can freak out if they feel threatened. They will attack dogs and other critters (even people) who get in their way or corner them. Like bears, I think it's a good idea not to surprise them.
And I seem to be able to sleep thru the sound. I guess it sounds like the old time night watchman calling out "all's well" every so often.