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Let's learn about vibrations and sound.

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Watch and learn

Watch this video to find out how vibrations and sounds are related.

Video

How do vibrations help us hear sound?

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What are vibrations?

A mobile phone with vibrations emanating from it.

are tiny shaking movements that go back and forth in a material.

Tip: Think of a mobile phone vibrating when receiving a phone call! Even if the phone is on silent, the vibrations still make a sound.

A mobile phone with vibrations emanating from it.

Vibrations can be produced in lots of different ways.

Hitting a tin with a spoon makes a loud clang.

Examples:

  • hitting two objects together

  • plucking a tightly stretched wire or string

  • pushing air through a tight space

  • rubbing certain objects together

Hitting a tin with a spoon makes a loud clang.

Are sounds vibrations?

Illustration of an orange wave form against a purple background.

Yes!

Sounds are vibrations.

They travel out from a source as waves.

Illustration of an orange wave form against a purple background.

The vibrations from the source make the molecules around them vibrate (shake and wobble) too.

Vibrations can travel through different things (solids, liquids and gases) to our ears馃憘

Our brains 馃 then make sense of what we are listening to.

Left to right: drums banging, ear, brain, thought bubble with the drums.
A marble bounces off a surface. Sound waves ripple out in all directions.

Did you know?

Sound waves spread out in all directions from the source, just like ripples from a stone thrown into a pond. That鈥檚 why you can hear someone banging a drum wherever you are in the room.

The sound waves get weaker as you get further away from the source and so the sound gets quieter.

A marble bounces off a surface. Sound waves ripple out in all directions.
Girl playing drum against coloured background.

A drum is an excellent sound-making object. The skin of the drum is stretched very tightly over the body of the drum. When the skin is hit, it vibrates and produces sound.

Hitting the drum harder, with more energy, makes a louder sound. The sound waves are larger and spread out further, carrying the sound a greater distance.

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Sound

Sound is defined by:

  • : how loud or quiet the sound is

and

  • : how high or low the sound is

These two things are not connected. A high-pitched sound can be loud or quiet, as can a low-pitched sound.

Pitch

The pitch of a sound is determined by the speed of its vibration.

It is measured in . This tells you how many vibrations happen in one second.

Image gallerySkip image gallerySlide 1 of 2, , A roar: a low-pitch sound A slow vibration such as a lion roar (between 40 鈥 200Hz) produces a low-pitched sound.

Try this

A boy touches his throat as he hums.
  1. Rest your hand on your windpipe.

  2. Hum a tune.

Can you feel the vibrations? As you change the pitch of your humming you will feel the vibrations change speed.

A boy touches his throat as he hums.

( Humans make sounds by pushing air out of our lungs through a pair of vocal folds in our windpipe. The vocal folds cause the air to start vibrating and the sound is shaped by the mouth into recognisable sounds such as speech! )

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Activity

Challenge

Make an elastic band guitar!

You will need:

  • a show box or plastic food container

  • elastic bands of different lengths and widths

  • protective glasses

Watch the video below for instructions

Video

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Key words

鈥 Tiny movements back and forth in a material.

(Hz) 鈥 The units of measurement of pitch. 100Hz means 100 waves per second.

鈥 How loud or quiet a sound is. Measured in decibels.

鈥 How high or low a sound is. A whistle is high pitched and thunder is low pitched.

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Quiz

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More on Light and sound

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