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The Sound Unit
Sound energy needs a medium to travel through.
Solids, liquids, and gases conduct sound.
Sound will not travel in a vacuum, a space with no
matter.
Sound is a form of energy that travels in waves.
All sounds are created by vibrations.
Vibrations cause a movement of air molecules called a sound
wave.
Sound waves travel as longitudinal waves with areas of compression (tightly packed air molecules)
and areas of rarefaction (air molecules spread apart).
compression rarefaction
The crests of these waves are areas of high density, called compressions. The troughs are called rarefactions.
Sometimes sound waves are shown as a transverse wave. Light and heat are actually transverse waves, not sound. We use the transverse wave because it is easy to study. crest
trough
amplitude
wavelength
Wavelength - the distance between two waves Crest - the top of a wave
Trough - the bottom of a wave
Amplitude - the height of a wave, a measurement of the amount of energy the wave is carrying. (loudness)
C
T
W A
Frequency - Vibrations or waves / second, measured in hertz
Pitch - How high or how low a sound is
transverse
longitudinal
transverse
longitudinal
A B
D C
Compare Waves 1. Which wave has a low frequency and low
amplitude?, high frequency, high amplitude?
2. Which wave has a steady amplitude but changing frequency?, steady frequency but changing amplitude?
Liquids transmit sound faster than gases. Sound travels 4-5 times faster in
water than in air.
Sound travels 15 times faster
through steel than air. Why??
760 miles/hour
1mile in 5 seconds
The Speed of Sound
Air @ 70 degrees F 340 m/s
Air @ 30 degrees F 300 m/s
H2O 1500 m/s
Brick 3700 m/s
Steel 5200 m/s
SPEED OF LIGHT
300,000,000 Meters /second (remember sound? 340 meter/sec.)
Light can travel 7 times around the world in 1 second. WOW!
This is about 180,000 miles per second.
neeerrrrrrooooooooooooooooooommmm
Doppler Effect - The apparent change in the pitch of a sound created by a moving object.
Breaking the Sound Barrier
An aircraft traveling at close to the speed of sound catches up to its own sound waves. These waves form a wall of compressed air called the sound barrier.
A sonic boom is created by any craft that travels faster than the speed of sound. The loud crack is created by super compressed air.
Human Hearing Range 20 – 20,000 Hz Infrasound is any sound below our hearing range
Ultrasound is any sound above our hearing range
http://www.phys.unsw.edu.au/jw/hearing.html
http://www.ltscotland.org.uk/5to14/resources/science/oscilloscope.asp
ULTRASOUND High frequency waves are used to show images inside patients.
This could be your first baby photo.
Today’s ultrasound is high definition.
Ultrasound is used for:
• Diagnosis of an injury.
• Treatment for pulled ligaments and muscles.
More uses for Ultrasound:
Illness or pregnancy of a Horse
Research about Turtles
Animals benefit too - it’s painless.
Echo - A reflected sound wave.
Echolocation - Animals that use reflected sound waves to search for prey or to find their location.
Echolocation:
In the air
and water.
Sonar -Sound Navigation and Ranging Electronically produced ultrasonic
waves are sent out and reflected off of objects below. The reflected waves provide an image of underwater objects.
Work slide
SONAR - used to locate sunken ships
FISH FINDERS AND ECHO SOUNDERS
different shapes and sizes
Resonance – Vibrations traveling through a material match that materials natural frequency.
Decibel level of common sounds
Decibel – The unit used to measure sound loudness.
Noise – any unpleasant or unwanted sound, usually with an irregular wave pattern.
A
B
Engineered Solutions to Controlling Noise Pollution:
Acoustics
How do we hear these vibrations called sound?
Outer Ear-Pinna
The Ear
Outer Ear
Pinna - Collects sounds waves and funnels them inward.
Auditory Canal - Lined with tiny hairs, the auditory canal filters out unwanted particles. Ear wax helps with this process. Also, the canal provides a passageway for sound to take.
Middle Ear Ear Drum (tympanic membrane) - As sound waves hit the ear drum they are turned back into vibrations.
Healthy
Infected
Perforated
Tubes
3 Bones (Malleus Incus Stapes) - These bones pass vibrations from the
eardrum to the inner ear.
Inner Ear Cochlea - This snail shaped organ is filled with fluid and lined with hair. It turns vibrations into electrical messages.
Neurobiology of the Cochlea
http://www.blackwellpublishing.com/matthews/ear.html
http://www.hhmi.org/biointeractive/media/cochlea-lg.mov
Semicircular Canals – the fluid inside of these organs moves and sends messages to your brain to help you keep your balance.
Work slide
Relative loudness of common sounds
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