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SOUND WAVES
A. Sound waves are longitudinal.
B. Sound waves are mechanicalthey need a medium and a
vibration.
C. Sound does not travel in a
vacuum.
Sound Waves
VELOCITY OF SOUND
At STP sound travels 3.31 x 102m/s
> It’s 4 times faster in water.
> It’s 15 times faster in metal.
Will change due to temperature:
v = 331m/s + 0.6(T)
(T is in Celsius)
Sound is a range of wave frequencies that
the ear is sensitive to. (20Hz- 20,000Hz)
Infrasonic sound- Sounds lower than 20Hz
Ultrasonic sound- frequencies higher than
20,000Hz
Transmission Range- frequencies an
organism can produce ( humans 851000Hz)
Hearing Ranges
How does the ear work?
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
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The outer ear “catches the sound waves”.
The middle ear takes the sound waves and
“vibrates” the eardrum.
The inner ear sends the messages to the brain.
Middle Ear
Outer Ear
Inner Ear
http://www.youtube.com/watch?v=pCCcFDoyBxM
Talking
• http://www.youtub
e.com/watch?v=Jz
yHKYQzPBk
• http://www.youtub
e.com/watch?v=dXbjFn3aqE
FREQUENCY
Frequency- the
number of vibrations
per second. How
the ear identifies this
vibration is called
pitch. Pitch and
frequency are
directly proportional.
http://www.animations.physics.unsw.edu
.au/jw/sound-pitch-loudness-timbre.htm
High Pitch
Low Pitch
FUN INFO
The phone company uses a
combination of frequencies
to make a unique sound for
each number on the phone.
#1 is 687Hz and 1209Hz
#2 is 687Hz and 1336Hz
#3 is 687Hz and 1477Hz
http://soundbible.com/tags-dial.html
AMPLITUDE
Amplitude- the maximum
displacement of the
particles from
equilibrium. Amplitude
determines the
intensity of the sound
and how loud it is.
http://www.animations.physics.unsw.edu.au/jw/sound-pitch-loudnesstimbre.htm
SOUND INTENSITY
Sound Intensity- the
rate of flow of sound
energy from a
source. Measured
in decibels or
watts/meter2
According to OSHA
85dB and higher will
produce permanent
hearing damage.
HOMEWORK
• FROM TEXT BOOK
pg 369 #21-23 and #25-30
Show all formula’s and
calculations!