I'm listening to my dog Taullulah nibble on a bone, and it's just making me smile and think about how my ears have developed the ability to distinguish acceptable things such as bones from unacceptable things such as tubes of lip balm and clip-on ukulele tuners.

My mind throws up red flags when the pitch is too high. The cracking sound almost always means that she's chewing on contraband, because chew toys don't make that high-pitched cracking sound. Pens make that sound, as do markers, small picture frames, power adapters, and countless other items made of plastic.

Right now I'm just filing away in my mind the way that I feel when I hear that cracking sound. That feeling, the way I feel the slight tingle in the backs of my ears…it's that physical feeling I get when something's wrong.

It's good to become familiar with that feeling, because other things besides a dog's teeth on plastic can trigger it. I feel it when I listen to someone in power tell me that it's all good, that I can trust them. Then I know: it's not the soothing sound of teeth on a rawhide chew toy.