Hearing through our bones

Roll up your sleeves to expose the tip of your elbow.
Push one pointer finger against the flap that closes your ear (the tragus).
With your other hand, pick up the tuning fork by the handle end.
Hit the branched end of the tuning fork hard on your knee or a surface that will not get damaged.
Press the ball of the tuning fork against your elbow bone.
Can you hear the note from the tuning fork? If you can't, try hitting the tuning fork harder and pressing your finger more firmly into your ear.

With someone to help you, you can also hear the sound if the ball of the tuning fork is pressed against your forehead, your chin, or other bone in your head. Block both ears, while your partner presses the vibrating tuning fork against one of your bones. How far away from your head can you place the vibrating tuning fork and still hear it?

For younger students, ask them to push closed the flaps in both their ears, and point their elbows towards you. The teacher handles the tuning fork.

The sound vibrations from the tuning fork travel through your bone and directly to your inner ear. We usually hear sounds through the air, which are received by our outer ear (our ear flaps) before being transferred to our inner ear.

Snakes do not have outer ears. Sound vibrations from the ground vibrate their jaw bones, which transmit the sound vibrations to their inner ear directly (as in this activity).
They are very sensitive to sounds made by small prey running nearby.

Whales hear low frequency sounds, that have travelled a long way through the ocean, through the bones of their skull.