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

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

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!

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

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

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

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

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

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

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 http://www.bbc.co.uk/wiltshire/content/articles/2006/04/04/mosquito_sound_wave_feature.shtml http://www.jetcityorange.com/MosquitoRingtone.html

Frequency on the Oscilloscope High pitched (frequency) waves are close together Dolphin (http://www.geocities.com/CapeCanaveral/1046/audio1.html) Low pitched (frequency) waves are spread apart Both waves are equally loud (because they are the same height)

Our Ear

The Ear

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

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

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

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

Wavelength and Frequency High pitched sounds have a high frequency and a short wavelength http://www.acoustics.salford.ac.uk/schools/index1.htm