What causes sound? · 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

What causes sound?

How does sound travel?

© cgrahamphysics.com 2016

Can you guess

the sounds?


How many did

you guess right?


Aim

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

sounds

Keywords • Amplitude, frequency, pitch, sound,

cochlea, eardrum, decibel


http://www.firstpeople.us/FP-Html-Pictures/wolves_pg2.html

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.


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?


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

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


How does sound travel through the air?


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


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


Good vibrations!

What vibrates so that each of these objects makes sound?

harp strings

lute strings

drum skin

mouth blowing horn


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


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


8l - Sound - 01 - Movie Sound travelling through air.mpg

8l - Sound - 01 - Movie Sound travelling through liquid.mpg

8l - Sound - 01 - Movie Sound travelling through solids.mpg

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.

ears, vibrations, molecules © cgrahamphysics.com 2016

Describing Sound Sounds can be quiet or loud.

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


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


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


Documents

What causes sound? · 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