Lesson 1
Sound
Can you guess what these sounds are?
Beluga Whale
Shrimp
SOUND
What is sound?
• Sound is a form of
energy
• Sound energy can be
converted into other
energy forms
Sound energy
Sound energy
Kinetic Energy
Sound energy (contd.)
Sound energy can be converted into other energy forms
Sound energy
Electrical energy
How is sound created?
Sound is created when objects vibrate
Vibrations
• Sound is produced by vibrations of the air molecules
• A sound wave is just a moving pattern of changes in
air pressure
What is a sound wave?
Sound wave
Vibrating ruler
Pressure
Compression
Rarefaction
Time
Transmission of sound
• Sound requires a medium in order to be transmitted
• Sound can be transmitted through a solid, liquid or
gas
• Sound cannot travel in a vacuum
Non-mandatory experiment to show
Sound needs a medium in which to
travel
What are echoes?
• Sound can be reflected
off surfaces
• Echoes are sounds that
are reflected from a
surface
• Sound reflection can be
used to calculate
distance
How do bats use sound?
Echolocation
Lesson 2
What is the speed of sound?
• Speed of sound differs
in different materials
• Speed of sound in air at
average temperatures
and average pressure is
approximately 340m/s
Speed of sound (contd.)
• Sound does not travel through all materials at the
same speed
• Sound travels through water at approximately
1500m/s
• Sound travels through iron at approximately 6000m/s
The speed of sound and the speed of
light
• Speed of sound is much
smaller than the speed
of light
• Speed of sound
350m/s
• Speed of light
300 000 000m/s
• Calculate the distance
by counting the seconds
Seeing an event before we hear it
• Fireworks
• Waves crashing on a beach
in the distance
How do humans create sound?
• Sound is produced by air rushing from your lungs
past your vibrating vocal chords
• These vibrations caused fluctuations in the
rushing air, which formed a sound wave
How do we hear sound?
•
The vibrations travel through the air to our ears
•
Our eardrums vibrate with the sound
•
The vibrations are passed on through the ear,
changed to electrical energy and transmitted to the
brain
•
The brain then interprets and gives the sound
meaning
Sound
Can you guess what these sounds are?
Frog
Humpback whale
Hearing Damage
How much sound causes permanent damage?
140
1 minute
120
15 minutes
100
Below this level
(70dB) – hearing
damage
negligible
80
60
40
20
0
dB
Sound Level is measured in Decibels
Source of sound or noise
Jet taking off at distance of 30m
Sound level
(in decibels)
140
Threshold of pain
Disco loudspeaker 3m away
Pneumatic drill at road works 10m
away
Busy street traffic
Ordinary conversation
120
120
100
Average whisper
Threshold of hearing
20
0
70
60
Noise Protection
• Mandatory ear protection
• Ear muffs or ear plugs
• Required in certain work
environments where sound >
70dB
Assessment of student understanding
• Combination of homework and a class quiz
Homework
• An automatic focus camera is able to focus on
objects by use of an ultrasonic sound wave. The
camera sends out sound waves which reflect off
distant objects and return to the camera. A sensor
detects the time it takes for the waves to return and
then determines the distance an object is from the
camera. If a sound wave (speed = 340 m/s) returns to
the camera 0.150 seconds after leaving the camera,
how far away is the object?
Class Quiz - Sound
1.
2.
3.
4.
5.
6.
7.
8.
What is sound?
Give an example of sound energy being converted
into another energy form?
How is sound produced?
What does sound need in order to be transmitted?
Why is there no sound in a vacuum?
What is an echo?
What is name used for the technique whereby
some animals use sound for location?
What is the approximate speed of sound in air?
Class Quiz – Sound (contd.)
9.
The speed of sound in air can change with changes
in __________ and ___________ ?
10. Through which of the following materials would
sound travel faster (a) air, (b) water (c) iron
11. Why does sound travel faster in iron than in air?
12. During a storm a person hears the thunder before
seeing the lightening, Why?
13. Why do people who work in noisy environments
wear ear protection?
BIBLIOGRAPHY
• Websites
• http://www.acoustics.salford.ac.uk/schools/lesson4/fl
ash/waves1.swf
• http://www.colorado.edu/physics/phet/webpages/simulations-base.html
• http://www.coolnotions.com/AGifs/AGifs.htm
• http://www.findsounds.com/ISAPI/search.dll
• http://www.gifanimations.com/action/ImageDisplay?gr
oup=2&category=155&index=29&dir=stay
• http://www.harrythecat.com/graphics/b.html
BIBLIOGRAPHY (contd.)
• Http://www.juniorscience.ie
• http://www.oceanlink.island.net/oinfo/acoustics/AcousticAccompl
ish.html#Anchor-The-49575
• http://www.partnersinrhyme.com/soundfx/carsoundfx.shtml
• http://www.physics.brown.edu/physics/demopages/Demo/waves
/demo/3b3030.htm
• http://science.howstuffworks.com/hearing1.htm
• http://www.sounddogs.com/searchresults.asp
• Textbook – Exploring Science , 2003
O’Callaghan, M., Reilly, S. and Seery A., The Educational
Company