What causes sound?

How does sound travel?

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Can you guess

the sounds?

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How many did

you guess right?

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Aim

• To explain how sound travels • To use scientific words to describe

sounds

Keywords • Amplitude, frequency, pitch, sound,

cochlea, eardrum, decibel

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Word Meaning

intensity The loudness or volume of a sound. pitch How high or low a note sounds. vibrate Move backwards and forwards. amplitude Half the height of a wave. frequency The number of waves each second. hertz (Hz) The unit for frequency. 1 hertz means one

wave per second. loudness How loud a sound is; the volume of a

sound. oscilloscope An instrument which shows a picture of a

wave on a screen.

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Listen to the tuning fork, what do you observe?

The tuning fork vibrates and you hear a sound.

All sounds are caused by vibrations.

What causes sound?

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• For a sound to travel the vibrations must be passed on

• Sound is produced by a vibration and travels as a longitudinal wave

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How does sound travel through the air?

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If we connect an mp3 player to a speaker, we can all

hear the sound produced.

‘Seeing’ sound waves

If we also connect an oscilloscope to the mp3 player then

we can ‘see’ the sound waves.

speaker oscilloscope

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How sound travels…

1) An object makes a sound by vibrating

2) The vibrations pass through air by making air molecules vibrate

3) These vibrations are picked up by the ear

Air molecules

4) The ear then sends a message to the brain

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Good vibrations!

What vibrates so that each of these objects makes sound?

harp strings

lute strings

drum skin

mouth blowing horn

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Sound waves are vibrations and so need a substance to travel through.

With air inside, the sound can be heard.

With nothing inside [a vacuum], the sound can’t be heard.

What happens when the air is removed from the bell-jar?

Bell Jar Demonstration

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Travelling sound

Sound travels by particles vibrating. To understand this better you need to remember what the particles look like in a solid, liquid and a gas:

Gas Liquid Solid

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Cup Telephones

One person from each group of two should get a telephone from the bench.

Answer in full sentences:

How is the sound being transmitted to your ear?

Can you hear sounds that would be inaudible from a distance?

If so why?

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Making Sound

Sound is caused by __________.

These vibrations make nearby ________ vibrate, which make the molecules next to them vibrate passing the sound along to our _____.

So if there are no particles sound will not travel.

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Describing Sound Sounds can be quiet or loud.

Sounds can have different pitches (they can be high or low)

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1

2

3

4

5

6

7

8 camel

owl

sealion

monkey

harp

tapdancer

organ

siren

a) What is it? b) Is it high or low pitch

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What Causes Sound? recap

Aim

To explain how sound travels

To use scientific words to describe sounds

Plenary

Write down a small paragraph explaining how sound travels and why it travels differently in solids, liquids, gases and vacuums

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