Sound 120

anvil - (also called the incus) a tiny bone that passes vibrations from the hammer to the stirrup.

cochlea - a spiral-shaped, fluid-filled inner ear structure; it is lined with cilia (tiny hairs) that move when vibrated and cause a nerve impulse to form sounds.

eardrum - (also called the tympanic membrane) a thin membrane that vibrates when sound waves reach it.

Eustachian tube - a tube that connects the middle ear to the back of the nose; it equalizes the pressure between the middle ear and the air outside. When you "pop" your ears as you change altitude (going up a mountain or in an airplane), you are equalizing the air pressure in your middle ear.

hammer - (also called the malleus) a tiny bone that passes vibrations from the eardrum to the anvil.

nerves - these carry electro-chemical signals from the inner ear (the cochlea) to the brain.

outer ear canal - the tube through which sound travels to the eardrum.

pinna - (also called the auricle) the visible part of the outer ear. It collects sound and directs it into the outer ear canal

semicircular canals - three loops of fluid-filled tubes that are attached to the cochlea in the inner ear. They help us maintain our sense of balance.

stirrup - (also called the stapes) a tiny, U-shaped bone that passes vibrations from the stirrup to the cochlea. This is the smallest bone in the human body (it is 0.25 to 0.33 cm long).

Limits of audiability

We cant hear all frequencies, at the lower end something with a frequency of < 35 Hz actually sounds like 35 individual sounds per second. Above this limit the sound actually seems like 1 ongoing note, frequency. The human ear has a wide spectrum of frequencies that it can hear, it does not hear all these frequencies at the same level, even if the sound meter measures them all to be of the same power. This is because the ear reacts to some frequencies more readily than others. As we continue to increase the frequency of the sound we will notice that young people can hear higher frequencies than older people, for some young people the upper limit of hearing can go up as high as 22,000 Hz (22kHz) as we get older this upper limit might fall as low as 18,000 Hz (18kHz).

This is used in some places to deter young people from loitering in those vacinities, while it has little or no effect on the older generations.

This should be demonstrated in class using a signal generator,

You will notice that sounds at certain frequencies feel louder but the actual power in the wave is the same.

If you increase the amplitude (Volume of Power) coming from the generator

And you should check out this site that has a similar test on it

http://theoatmeal.com/quizzes/sound/

if you do go to this site click on random cartoon link ..... can be good / can also disappoint

Power of sound and it effect on humans