Grade 3 (age 8-9)

Properties of Sound

Sound is created when an object vibrates, and the shaking travels through the air to your ears. Hit a drum hard for a loud sound or gently for a quiet one, and short and long strings give different pitches. Sound can travel through water and wood too, not only through air. Here you can change how big and fast the vibration is and watch how the sound changes.

Sound is Vibration

Vibration Speed50

🎵 How is Sound Made?

①Objects must vibrate to make sound

②Plucking a guitar string makes it vibrate

③Hitting a drum makes the skin vibrate

④Vibration travels through air to your ear

Pitch and Loudness

Pitch (frequency)50

Loudness (amplitude)60

💡 High Pitch vs Loud Sound

①Fast vibration (high frequency) → high pitch

②Big vibration (high amplitude) → loud sound

③Flute = high, drum = low

④Whisper = soft, shout = loud

Summary

Pitch of Sound

Fast vibration → high pitch / slow → low pitch

Many vibrations per second = high pitch

Loudness of Sound

Big amplitude → loud / small → soft

Bigger vibration width = louder sound

🎯 Key Points

①Sound = vibration of objects

②Fast vibration = high pitch, slow = low pitch

③Big vibration = loud, small = soft

④Sound travels through air

⑤No sound in vacuum (no air)

Examples and Unit Test

Example 1

Why does a sound come out when you pluck a guitar string or hit a drum?

Sound is made when an object vibrates.

The guitar string or drum skin vibrates, and that vibration travels through the air to your ear, so you hear sound.

▸ Because the object vibrates (the vibration travels through the air)

Sound is made by the vibration of an object.

Example 2

To make a sound higher, and to make it louder, how should the vibration change?

The faster the vibration (the higher the frequency), the higher the sound.

The wider the vibration (the larger the amplitude), the louder the sound, so pitch comes from speed and loudness from amplitude.

▸ Higher sound = faster vibration / louder sound = wider vibration

A higher frequency means a higher sound; a larger amplitude means a louder sound.

Unit-test style

Which statement about the properties of sound is correct?

①Sound is made when an object vibrates

②The slower the vibration, the higher the sound

③The smaller the amplitude, the louder the sound

④Sound travels well even where there is no air

⑤Sound is made without any vibration

▸ ① Sound is made when an object vibrates

Sound is made when an object vibrates, and the vibration travels through the air.

A faster vibration makes a higher sound (②), a larger amplitude makes a louder sound (③), sound does not travel in a vacuum (④), and sound needs vibration to be made (⑤).

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