Resources
Resources
Background information
What is sound?
Sound is made when something moves backwards and forwards (vibrates) very
quickly. The vibration sends a compression wave through the air. When that
compression wave reaches our ear drums it makes them vibrate too, which in turn is
amplified by the middle ear, encoded by the cochlea and sent as a nerve message to
our brains. Our brains interpret the vibration of our ear drums as sound.
How does a compression wave travel through the air?
When an object vibrates it moves the air particles around it. As the object moves one
way, the air particles receive a push, which compresses the air, a bit like the push
you give to air when you pump up a bicycle tyre. The pushed air particles bump into
the air particles next to them and a wave of compressed air passes out from the
object. When the object moves the other way, it creates an area of low pressure,
which pulls the air particles towards it. This creates a wave of low pressure. The
alternating pulses of high and low pressure move out in all directions from the source
of the sound. Our eardrums vibrate when these tiny pulses of pressure reach them.
A slinky can provide a model of a compression wave. Stretch the slinky out between
two people. One person pulls a bunch of coils tight towards them and then releases
them. The compression wave travels down the spring.
Sounds can carry through air because the air particles move to and fro and carry
sound compression waves. However, when there is no air, such as in a vacuum,
there are no air particles to carry the sound waves. When astronauts on a space walk
want to talk to each other, they cannot talk normally because there are no air
particles to carry the sound waves - they have to use radios instead.
The speed of sound in air
Sound waves travel in air at approximately 332 metres per second. The speed of
sound is even faster at higher temperatures because the air particles move faster
and collide more frequently. For each degree of increase in temperature the speed of
sound is increased by 0.6 metres per second.
The speed of sound in liquids and solids
Sound waves travel faster and more effectively in liquids than in gases and travel
even faster in solids. This is because the molecules of solids are more tightly packed
together than in liquids, and those in liquids are more tightly packed than in gases.
Vibrating effects are more easily passed on from one molecule to the next when they
are close together. The string of the string telephone is a solid through which the
vibrations of the speaker's voice are transferred quickly and effectively - much more
effectively than if the speaker had talked through the air to the other person.
http://www.museumvictoria.com.au/education/
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Resources
Websites for teacher reference and student research
Questacon Strike a Chord education materials includes additional physical science,
psychological and physiology activities
www.questacon.edu.au/html/strikeachord.html
The human ear
www.questacon.edu.au/html/assets/pdf/strike_a_chord_ear_relay.pdf
www.yale.edu/ynhti/curriculum/units/2000/5/00.05.x.html
www.aboutchildrenshealth.com/library/weekly/aa042600a.htm
http://stuffo.howstuffworks.com/hearing.htm/printable
www.hearing.com.au/hearing_health_ear.htm
How sonar actually works www.exploratorium.edu/theworld/sonar
An excellent classroom activity to understand the principles of echo communication
www.accessexcellence.org/AE/AEC/AEF/1995mills_echo.html
Listen to dolphins and bats www.biosonar.bris.ac.uk/index.htm
Possible influence of human-made noise pollution on animals in the world of sound
www.exploratorium.edu/theworld/sonar/
www.questacon.edu.au/html/assets/pdf/strike_a_chord_hearing_ranges.pdf
Find out the sound range of different mammals (including humans)
www.questacon.edu.au/html/assets/pdf/strike_a_chord_hearing_ranges.pdf
www.lsu.edu/deafness/Hearingrange.html
Find out about how fish hear
http://www.earthsky.com/teachers/articles/articles.php?id=6&p=2
http://www.mote.org/~kevin/vtour/fishfaqsear
Find out about how insects hear
http://www.4to40.com/earth/geography/index.asp?article=earth_geography_insects
http://monitor.admin.musc.edu/~cfs/learning/InsectSenses.pdf)
http://www.earthlife.net/insects/anatomy.html
Cool Science for Curious Kids; information and experiments about general science
http://www.hhmi.org/coolscience/
Simple physics demonstrations to do in the classroom
http://sprott.physics.wisc.edu/demobook/chapter1.htm
Exploratorium; simple science experiments with simple explanations
http://www.exploratorium.edu/snacks/snackintro.html
Find out more about just about anything, with explanations accompanied by good
diagrams and animations with How Stuff Works
http://www.howstuffworks.com/
.
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