Did you hear that SOUND?

Sound is a form of energy that travels in

waves.

What makes Sound?

1. Vibration: back and forth motiona. There can not be sound if there

is not any vibrationb. Most vibrations are too fast for

you to see.c. Vibrations require energy—

sound is a form of energy.

How does Sound Travel?

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

What Forms of Matter can Sound Travel Through?

1. Gas: sound travels easily through gasesa. 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).

Sound Reflection and Absorption

A. Reflected sound is called an echo.1. The vibrations are

reflecting back to you.B. Soft, air-filled objects absorb sound.

1. When sound is absorbed, you do not hear it because it is not reflected back to you.

1. Sound Waves

A. Sound vibrations occur in waves that go out in every direction like a circle.

1. Sound waves are created by repeated patterns of molecules spreading apart and squeezing together.

B. Sound Waves have 3 common features:1. They:

a. Have a set wavelength b. Vibrate at different speeds

--Frequency: the number of complete wavelengths, or times an object vibrates per second.

c. Carry Energy--amplitude is the amount of energy a wave has--high amplitude sound is

made by objects with great vibrating motion

Pitch

1. Pitch: how high or low a sound isa. 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

Making and Hearing Sounds1. Hearing Sound

a. Humans have two ears on opposite sides of their heads. Each ear gathers sound waves on each side of your body.b. There are two ways that humans hear sounds.

» With your ears.» With your brain.

How do you hear sound?

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, moves to the anvil, and finally the 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.

2. Making Sound• All sounds are made by vibrations.

• Humans make sound waves by using their voice.

• The human voice is also 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.

How do the vocal cords produce 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.

Communication tools that use sound

• 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.

• Animal sounds• Musical instruments