A strange model of the ear

 

I made a functional model of an ear. The funnel is the pinna, focussing the waves into the cardboard tube that represents the ear canal. This takes the vibrating air inside the head where it hits the ear drum, represented by a stretched balloon. The whiteboard pen represents the ear bones and a balloon filled with water represents the cochlea with the wires representing the auditory nerve. The ear bones are necessary because when sound travels through gas to hit liquid most of it is reflected. This is why in an ultrasound scan, gel is put between the transducer and the body. In the ear, the bones act to stop this happening. I've seen it called an example of impedance matching. The way that the bones act as levers also magnifies the oscillation so in a sense the bones act as an amplifier.