Science · Chapter 9 · ICSE Class 5

Sound

Sound is created by vibrations, and every sound has a pitch and a volume. Drag the sliders and watch the sound wave change shape.

The Sound Wave Machine
A medium pitch, medium volume sound.
Medium
Medium

Try it: high pitch makes tight, close waves; loud volume makes tall waves.

9.1

What is sound?

Sound is a form of energy produced when an object vibrates — moves rapidly back and forth. These vibrations travel outward and our ears detect them as sound.

Try this — Stretch a rubber band and pluck it — you can both hear and feel it vibrating. Stop the vibration by holding it still, and the sound stops too.
9.2

How does sound travel?

1Sound needs a medium

Sound travels through a medium — a substance like air, water, or a solid. It cannot travel through empty space (a vacuum) because there are no particles to carry the vibrations.

2Sound through different mediums

Sound travels fastest through solids, slower through liquids, and slowest through air (gas), because particles are packed closer together in solids.

9.3

Loud, soft, high, and low sounds

Loud sound
Large vibrations

Has a large amplitude (height of the wave).

Soft sound
Small vibrations

Has a small amplitude (height of the wave).

High pitch
Fast vibrations

Has a high frequency — vibrations happen quickly.

Watch out — Loudness and pitch are two different things! A sound can be loud AND low-pitched (like a bass drum), or soft AND high-pitched (like a quiet whistle) — one doesn't decide the other.
9.4

Noise pollution and protecting our ears

Very loud or unwanted sound is called noise pollution, and it can harm our hearing over time. Loud traffic, construction, and blasting music are common sources. We can protect our ears by keeping the volume down and avoiding prolonged exposure to very loud sounds.

Practice

Exercises

Tap a question to reveal its answer once you've tried it yourself.

Assess

Sample tests

Two 20-mark, 30-minute tests. Reveal answers question by question.