Sound 120

OP42 understand that the ear detects sound vibrations and that exposure to very loud sounds can cause damage to hearing

The Ear is a complicated organ that is more than the two bits of skin covered cartilage on the side of your head.

The ear is inside your skull, where the sensitive organs and tissues are somewhat protected from damage.

OP41 Sound requires a medium OP42 Sound and the EarOP43 The Speed of Sound OP44

once the sound wave enters the ear, goes past three small bones (no larger than your thumbnail), around a "snail shell", and an electric current takes the energy in to the brain. Travels at 100m/s, and most words can be processed b4 they have left the speakers mouth

the Cilia. Those tiny hairs are what transduce the wave forms from vibrating air particles to bioelectrical currents that travel to your brain.

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

Know which noises can cause damage. Wear ear plugs when you are involved in a loud activity.

85 Decibels

Prolonged exposure to any noise at or above 85 decibels can cause gradual hearing loss.

100 Decibels

No more than 15 minutes of unprotected exposure recommended.

110 Decibels

Regular exposure of more than 1 minute risks permanent hearing loss.

This is the sign to say wear ear protection!

If you see this sign, WEAR the ear protectors, you have been warned !

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