Sound is a form of energy that travels in waves.

1. Vibration: back and forth motion a. There can not be sound if there is not any vibration b. Most vibrations are too fast to see. c. Vibrations require energy— sound is a form of energy.

2. When something vibrates molecules in the air crowd together, then spread apart, causing sound waves to travel away from the vibrating object

1. Gas : sound travels easily through gases  It travels about 1,129 feet per second through air. (That’s how fast it travels when you talk!)

2. Liquids : Sound travels through water about 4,794 feet per second. (Think of what ripples look like in the water and how they spread.)

3. Solids : Sound travels through a solid like wood at a rate of 12,620 feet per second. * Sound travels fastest through solids! *

4. Sound cannot travel through a vacuum (a space that is “empty” of matter).

A.) Reflected sound is called an echo. 1. The vibrations are reflecting back to you. B.)Absorb sound is Soft, air-filled objects. 1. When sound is absorbed, you do not hear it because it is not reflected back to you.

Sound vibrations occur in waves that go out in every direction like a circle. Sound waves are created by repeated patterns of molecules spreading apart and squeezing together.

Sound Waves have 3 common features: 1.) Have a set wavelength 2.) Vibrate at different speeds -- Frequency: the number of complete wavelengths, or times an object vibrates per second. 3.) Carry Energy --amplitude is the amount of energy a wave has --high amplitude sound is made by objects with great vibrating motion

Pitch: how high or low a sound is a. The higher the pitch the more “squeezed” together the waves are b. The higher the pitch the higher the frequency c. The lower the pitch the lower the frequency

Humans have two ears on opposite sides of their heads. Each ear gathers sound waves on each side of your body. There are two ways that humans hear sounds.  With your ears.  With your brain. Hearing Sounds

1. Sound causes your eardrum to vibrate. The eardrum vibrates differently for each sound. 2.The bones of your ear begin to vibrate, beginning with the hammer, anvil, and stirrup. 3.The sound energy passes to the inner ear. This causes the fluid in the cochlea to move. 4.The nerves then carry the message to the brain. 5. Your brain then tells you what the sound is.

The Ear

 You may feel like you're hearing through cotton wool.  You might feel like your ears need to 'pop'.  You may hear ringing or high whistling  These effects may last for a few hours or even a few days after the loud noise has stopped, but some damage will last for ever if you listen to loud noise for too long or too often.

 Wear earmuffs or ear plugs if you have to be somewhere noisy (like a car race or using noisy power tools).  Wear earplugs as well as ear muffs if you have to be in a noisy place.  Turn the volume down and get used to listening to quieter sounds.

 All sounds are made by vibrations.  The source of sound in humans is the vocal cords.  Vocal cords — 2 thin, elastic, bands of tissue that vibrate to produce sound. Making Sound

1. Air from the lungs flows through the windpipe and into the voice box (where the vocal cords are). 2. Then the air pushes the vocal cords apart making them vibrate. 3. The vibrations create a series of sound waves that exit through your mouth. 4. The change of shape of the vocal cords changes the sound and its pitch. 5. If you can’t talk because of a cold or laryngitis, it is because your vocal cords are swollen and inflamed.

Voice – allows you to communicate with others. Morse Code – code for numbers and letters using sound Sonar – a device that sends sound waves through water to measure or find something. Musical instruments 