Sound


 * The Ear **
 * Your ears are in charge of collecting sounds, processing them and sending sound signals to your brain. But that's not all - your ears also help you to keep your balance.


 * The ear is made up of three different sections: **the outer ear, the middle ear, and the inner ear**. These parts all work together so you can hear and process sounds.

> curled tube in the inner ear. The cochlea is filled with liquid, which moves like a wave, when the ossicles vibrate. > sound reaches the cochlea, the vibrations (sound) cause the hairs on the cells to move, creating nerve signals that the brain understands as sound. The brain puts it together and hooray! You hear your favorite song on the radio.
 * The Outer Ear **
 * The **outer ear** is called the pinna or auricle (say: or-ih-kul). This is the part of the ear that people can see. It's what people pierce to wear earrings. The main job of the outer ear is to collect sounds.
 * The outer ear also includes the **ear canal**, where wax is produced.
 * Earwax is that gunky stuff that protects the canal. Earwax contains chemicals that fight off infections that could hurt the skin inside the ear canal. It also collects dirt to help keep the ear canal clean.
 * However, there is a problem if you have too much!
 * The Middle Ear **
 * After sound waves enter the outer ear, they travel through the ear canal and make their way to the middle ear.
 * The middle ear's main job is to take those sound waves and turn them into vibrations that are delivered to the inner ear.
 * To do this, it needs the eardrum, which is a thin piece of skin stretched tight like a drum.
 * The eardrum separates the outer ear from the middle ear and the ** ossicles ** (say: ** ah **-sih-kulz).
 * They are the three tiniest, most delicate bones in your body. They include: * the ** malleus ** * the ** incus ** * the ** stapes **
 * When sound waves reach the eardrum, they cause the eardrum to vibrate. When the eardrum vibrates, it moves the tiny ossicles.
 * These bones help sound move along on its journey into the inner ear.
 * The Inner Ear[[image:http://nyogmd.com/cms/files/how-ear-works.jpg width="308" height="204" align="right" caption="The Outer, Middle & Inner Ear"]] **
 * Sound comes into the inner ear as vibrations and enters the ** cochlea ** (say: ** ko **-klee-uh), a small,
 * The cochlea is also lined with tiny hairs that are so small you would need a microscope to see them. When

=Loudness of a sound= The loudness of a sound is how loud or soft the sound is. A guitar string plucked strongly makes a **loud** sound. A guitar string plucked gently makes a **soft** sound. A drum skin hit hard makes a loud sound. A drum skin hit gently makes a soft sound.

Loud sound
A recorder blown hard makes a loud sound.

Soft sound
A recorder blown gently makes a soft sound.

=Pitch of a sound= The **pitch** of a sound is how high or low the sound is. A high sound has a high pitch and a low sound has a low pitch. =Sound vibrations can travel through different materials= Sounds as vibrations can travel through many different materials.
 * A **short string** gives a **higher-pitched** sound than a long string when they are plucked.
 * A **tight drum skin** gives a **higher-pitched** sound than a loose drum skin.
 * Sound can travel through **solids**, like metal, stone and wood.
 * Sound can travel through **liquids**, like water.
 * Sound can travel through **gases**, like air.

Sound vibrations travel better through some materials than others. For example, sound vibrations travel very well along metal pipes.

Sound cannot travel through a completely empty space (a **vacuum**), which has nothing, not even air, in it. If there is a vacuum between a sound-making object and our ears, we won’t be able to hear the sound. = = =__Key Points__=
 * **Sound is caused by vibrations**
 * **Vibrating objects make sound. The sound is passed to our ears and this is how we hear**
 * **Sounds get louder (increase in volume) when they vibrate harder**
 * **Pitch is how high or how low a note is**
 * **The shorter the vibrating object, the higher the pitch**