A source of sound with a single, built-in speaker that is easy to reach, such as a radio or wind-up music box (for this Snack, sound makers such as boom boxes, with separated speakers, don’t always work well)
Sturdy plastic toothbrush with a solid plastic handle
To Do and Notice
Turn on the radio (or other sound source), and then put earplugs in your ears and adjust the volume low enough that you can no longer hear it.
Clasp one end of the toothbrush between your front teeth and touch the other end of the toothbrush to the radio near the vibrating speaker. You should be able to hear the radio again—but through your body instead of through the air!
What’s Going On?
When you hear sounds through the toothbrush, you’re actually hearing with many parts of your head. Vibrations from the sound source are transmitted through the hard plastic of the toothbrush into your teeth and jaw, then through the bones of your skull to the bones of your ear, and finally to the auditory nerve.
This works because bone is a relatively efficient conductor of sound, so it offers an alternate pathway for sound perception. People who have outer- or middle-ear problems may have trouble accessing and processing airborne sound vibrations, but for those whose auditory nerves can still process sound, devices that channel vibrations directly through the bones of the head can sometimes compensate for some hearing loss. Unfortunately, this method does not make up for noise-induced and age-related hearing loss.
In the late eighteenth century, when German composer Ludwig van Beethoven began to lose his hearing, he tried listening to his piano by clasping a wooden stick in his teeth and touching it to the piano. Two hundred years later, joggers can buy bone-conduction headphones—bluetooth-based systems that conduct sound through the cheek bones.