2. Sound Our ears magnify sound 20 times
Resonance is what makes opera singers break glass when they hit a high note. The frequency of the voice matches the vibrations of glass molecules making it break.
Folds in the wall absorb sound (making it quiet outside) and prevent echoes

3. How Are Sounds Made?
Sounds are made when objects vibrate (shake from side to side)
Loudspeakers can create large vibrations
Guitar strings vibrate
Drum skins vibrate
Air vibrates inside a recorder
Our vocal cords vibrate when we speak

4. How Does Sound Travel? Sound needs atoms to travel through
It can travel through solids, liquids and gases like air
It cannot travel through a vacuum
You would not be able to make noise in space!

5. The Speed of Sound The speed of sound through the air is 330 m/s
It is 1,480 m/s through water
It is 5,100 m/s through Steel
Through which state of matter does sound travel quickest?
Solids
Why?
The atoms are closer together, so they are more able to pass on vibrations

6. Thunderstorms The speed of light is 300,000,000 m/sec
Sound travels at 330 m/sec
Why do you see lightning before you hear thunder?
Light from the lightning is 1 million times quicker than sound
If you count from when you see a lightning flash to when you hear a clap of thunder and this takes 3 seconds. How far away is the storm?
3 x 330 = 990 metres

7. How do bats travel?
Bats cannot see very well, but they are superb night fliers.
They use echolocation to find food (moths)
They make a high pitched squeak that bounces off objects
These echoes tell bats whether they are about to fly into a tree or catch their dinner

8. Loudness Loudness is also called Amplitude
It is measured in Decibels (dB)
Rock bands uses Amplifiers to make their music louder
Big vibrations cause loud sound e.g. thumping a Lambeg drum

9. Amplitude on an Oscilloscope
An oscilloscope shows the shape of vibrations
Sound travels as waves
A quiet sound is like a very small wave
A loud sound has a large wave
Both the quiet and loud sounds are the same width

10. Trivia
The whispering gallery in St. Paul’s Cathedral can carry whispers 30m
The Doppler Effect is when sounds coming towards us get higher in pitch, but as they move away they get lower
The Eustachian tube allows air from the nose to equalise pressure on the ear drum

11. Pitch Pitch is also called frequency It is measured in Hertz (Hz)
Frequency is how fast something is vibrating
We cannot hear some high pitched sounds, like dog whistles
A deep voice (baritone) has a low pitch

12. Frequency on the Oscilloscope
High pitched (frequency) waves are close together
Dolphin (
Low pitched (frequency) waves are spread apart
Both waves are equally loud (because they are the same height)

13. Our Ear

14. The Ear

15. Our Ear Our audible range is between 20 – 20,000 Hz when we are young
As we get older this gets smaller
Loud sounds like aeroplanes taking off, jackhammers, mp3 players and rock concerts can burst our ear drums
Our ear drums can heal
If the cochlea is damaged our hearing is permanently damaged and we may need a hearing aid

16. The Audible Range of Different Animals
All the animals, except for the elephants can hear higher pitched sounds than us

17. Loudness of Sound Sound at 140dB can burst you ear drums
Mp3 players can go up to 100dB
Workmen using road drills wear ear protection

18. Ultrasound
Ultrasound scans are used on pregnant women to check on their baby
High pitched sounds are sent into the womb and reflect back from the foetus
Sonar scanning is used by trawlers to detect if there is shoals of fish beneath them
Submarines use sonar to detect wear the sea bed is

19. Wavelength and Frequency
High pitched sounds have a high frequency and a short wavelength