What happens to the sound wave?

[omega-centauri]

Ok so it happened again... my students asked a question I hand't thought of before (love it when that happens!) Can you help me?

What happens to the sound wave after it hits the eardrum? Does it get absorbed, or does it continue to go through your head?

I found lots of info about how the sound wave interacts with the ear, but then there's no info on if the wave continues after vibrating the ear drum (is there any energy left?) Any ideas are appreciated!

 

[Delta2]

I guess the soundwave continues deeper into the brain but it should attenuate fast and converted to heat. The portion of the soundwave that passes through the ear hole is very small and thus has very small energy (unless we talking for a soundwave of very big intensity/energy density, something like >150dB) and cannot damage the ear drum or the brain.

 

[Nugatory]

It's essentially all absorbed. Some of the energy in the energy in the wave goes to wiggling the little fibers in the inner ear to generate the nerve impulses that our brains interpret as sound. The rest of the energy ends up (as with just about all absorbed energy) as random bouncing around of the atoms in our heads, which is to say heat; the total amount of energy is so small that the amount of heat involved is completely unnoticeable.

 

[DaPi]

. . . and some will be reflected, n'est-ce pas?

 

[sophiecentaur]

Attached to the ear drum is a triad of tiny bones (the ossicles) which are essentially, levers. They are the equivalent of 'gears' or a transformer (in an acoustic sense) and they match the sound to another 'drum' on at the entrance to the inner ear. The sound vibrations are passed through all this mechanism and the matching network just described, ensures that a good amount of the sound energy gets transferred to the cochlea (a spiral of nerves attached to tiny hairs, each of which vibrates according to the frequencies contained in the incoming sound.
Matching is used throughout communications equipment and it takes many different forms, depending on what particular medium is being used. It's always a matter of improving the Signal to Noise Ratio as much as possible.

. and some will be reflected, n'est-ce pas?

Oh yes. There's always some degree of mis-match. (Fish and Whales have an easier job because the sound in water is already at a similar impedance to the sound in their wet tissues.)