? Library of Wonders   The Wonder of Sound

Why do dogs make odd sounds when they hear a police car’s siren?
Here’s a little quiz for you. Dogs make odd sounds when they hear a police car’s siren. What’s the reason for that? A: Because the siren is similar to a dog’s howl. B: Because dogs know some incident has happened. C: Because dogs get excited by the red flashing lights.

The right answer is A. But you are probably thinking a siren and a dog’s howl don’t sound much alike. So what’s going on? The reason is not the sound you hear, but how the air that carries the sound vibrates. Sounds reach our ears through vibrations in the air. The vibrations of air made by a siren are similar to the air vibrations when a dog howls. Long ago, when dogs still lived in the wild, they used to howl to each other to say things like: “This is my territory” or “Here I am”. So when dogs hear a police car’s siren, they mistake the siren for another dog howling and they can’t help but reply. Of course, it can get annoying when they howl at nighttime.