How do ear ossicles help in amplification even when there is synovial fluid present??

nishant34

The ear ossicles help in amplification of received sound (right?). We know that the joint between the three ear ossicles is synovial joint. Therefore, we have synovial fluid to prevent friction.

This synovial fluid should also help to reduce the intensity of the sound that is transmitted forward.

So how do we say that the ear ossicles help in amplifying the sound waves??

atyy

http://www.ncbi.nlm.nih.gov/books/NBK11076/
http://www.scientificamerican.com/ar...hammer-anvil-a

Darwin123

I am guessing here, based on physics. The bulk modulus of bone is much greater than the bulk modulus of water. The density of bone and water are more comparable. Therefore, the speed of sound in bone is probably much greater than the speed of sound in water.
Therefore, the speed of sound in the ossicles is probably much greater than the speed of sound in the synovial fluid. Thus, there is an impedance mismatch at the boundary between the ossicles and the synovial fluid.
Sound bounces off the boundary between ossicles and synovial fluid. So the ossicles serve as a pipe for transmitting sounds collected by the ear drums to the cochlea. In addition, the lever principle provides the amplification of the sound of the ossicles.
I think that the impedance mismatch between body fluids and hard bone is comparable to the impedance mismatch between air and body fluids.
Animals without ossicles often use other types of bone to get the sound to the cochlear. For instance, in some fish the air bladder collects sound. Some other skull bones lead the sound through the skull to the cochlear. In crocodilians, the jaw collects the sound and the jaw bone transmits the sound to the cochlear. There is usually some bone that leads the sound through the skull to the cochlear. Rarely does the path involve body fluid alone.

nishant34

THank you for your reply atyy and Darwin 123.

i really learnt a few more new things. Thanks!! :)