Science Year 4 Unit 6: Sound

What is Sound?

Vibrations

Sound is energy made

by vibrations. These

vibrations create

sound waves.

Sound Waves

Sound waves travel

through air, water, or

solids. They need a

medium.

No Air, No Sound

Sound can't travel in

space. There is no air

for the waves to move

through.

How Sound Travels: Waves!

1
Waves

Sound travels in waves, like ripples in a pond.

2
Compression

Particles are close together.

3
Rarefaction

Particles are spread apart.

Sound travels about 343 meters per second in air.

Sound Needs a Medium

Solids

Sound travels fastest through solids.

The particles are close together.

Liquids

Sound travels slower through liquids

than solids.

Gases

Sound travels slowest through gases.

The particles are far apart.

Experiment: Sound travels faster and efficiently through solids. Can you hear sound better through a desk or the air?

How We Hear Sound

1

Eardrum

Sound waves enter and vibrate the

eardrum.

2

Bones

Vibrations pass to tiny bones, which

amplify them.

3

Cochlea

The cochlea turns vibrations into

electrical signals.

4

Brain

The brain interprets signals as sound.

Parts of the Ear

Outer Ear (Pinna)

Collects sound waves.

Ear Canal

Passage to the eardrum.

Middle Ear Bones

(Malleus, Incus, Stapes) Amplify vibrations.

Cochlea

Turns vibrations into signals.

Loud and Soft Sounds:
Amplitude

1

Amplitude

How big the sound wave is.

2

Large Amplitude

Loud sound.

3

Small Amplitude

Soft sound.

4

Decibels (dB)

Measure sound intensity.

Sounds above 85dB can damage hearing.

High and Low Sounds: Frequency

1

2

3

4

Frequency

Waves per second.

Hertz (Hz)

Unit of measurement.

High Frequency

High-pitched sound.

Low Frequency

Low-pitched sound.

Changing Sounds

Pitch

Altered by length, thickness, or tension.

Loudness

Changed by increasing vibration force.

Activity: Make different sounds with a ruler. Change the vibrating length.

Recap: Sounds All Around!

3

Things to Remember

Sound is energy. It travels in waves. Ears turn vibrations into signals.

Experiment at home: Listen to different sounds. Describe their properties!