Sound wave

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Transcript Sound wave

DO NOW: 4/16
A radio wave broadcasts at
700 kHz and travels the
8
speed of light (3x10 m/s).
1.What is the period?
2.What is the wavelength?
PROPERTIES OF SOUND
4/6/11
SOUND WAVES
Sound
wave: a mechanical
wave transmitted through
matter (a material medium)
SOUND WAVES:
Sound
is a longitudinal wave:
PRESSURE VARIATIONS
Compression: particles closer together
 Rarefaction: particles farther apart

PROPERTIES OF SOUND: PITCH

Pitch: The sensation of a frequency
Higher
pitch! 

http://www.physicsclassroom.com/class/sound/U11l2a
.cfm
MUSIC
Consonant: Certain sound waves which, when played
simultaneously, will produce a pleasant sound
Interval
Frequency
Ratio
Examples
Octave
2:1
512 Hz and 256 Hz
Third
5:4
320 Hz and 256 Hz
Fourth
4:3
342 Hz and 256 Hz
Fifth
3:2
384 Hz and 256 Hz
EXAMPLE:
Two musical notes that have a frequency
ratio of 2:1 are said to be separated by an
octave. A musical note that is separated by
an octave from middle C (256 Hz) has a
frequency of _____.
a. 128 Hz
b. 254 Hz
c. 258 Hz
d. 345 Hz
e. none of these
REVIEW: AMPLITUDE

Amplitude represents energy
PROPERTIES OF SOUND: LOUDNESS
 Loudness
depends on the amplitude of
sound waves; measured in decibels (dB)
 Intensity (I): how loud a sound is in
relation to another
I  I i x10
# dB ' s
10
Source
Intensity
Level
# of Times Greater
Than TOH
Threshold of Hearing (TOH)
0 dB
100
Rustling Leaves
10 dB
101
Whisper
20 dB
102
Normal Conversation
60 dB
106
Busy Street Traffic
70 dB
107
Vacuum Cleaner
80 dB
108
Walkman at Maximum Level
100 dB
1010
Front Rows of Rock Concert
110 dB
1011
Threshold of Pain
130 dB
1013
Military Jet Takeoff
140 dB
1014
Instant Perforation of
Eardrum
160 dB
1016
EXAMPLE:
A mosquito's buzz is often rated with a
decibel rating of 40 dB. Normal
conversation is often rated at 60 dB. How
many times more intense is normal
conversation compared to a mosquito's
buzz?
a. 2
b. 20
c. 100
d. 200
e. 400
SPEED OF SOUND:
The speed of sound
depends primarily
on medium but also
on temperature:
v = 331 m/s + (0.6
m/s/C)•T
EXAMPLE:
Determine the speed of a sound wave in air
at a temperature of 20ºC.
v = 331 m/s + (0.6 m/s/C)•T
v = 331 m/s + (0.6m/s/C)•(20 C)
v = 331 m/s + 12 m/s
v = 343 m/s
ECHO:
echo:
a reflected sound; will
take twice the time to travel
the same distance
Example: a sound wave travels
500 m to a cliff, then returns to
where it started. If the sound
wave traveled 330 m/s, how
long does it take the sound to
return to where it started?
PRACTICE:
Use
the rest of class to
work on the worksheet
“Sound Waves.”
Be prepared to answer an
exit question at the end of
class
EXIT QUESTION:
Which property of sound is
determined by amplitude?
2. Which property of sound is
determined by frequency?
1.
DO NOW (4/17/12):
1. Which
property of sound is
determined by amplitude?
2. Which property of sound is
determined by frequency?
3. What is the velocity of
sound when the
temperature is 44˚ C?
AGENDA:
4th Q Project
 Homework questions
 Extra credit (optional)

FOURTH QUARTER PROJECT
 Deadline 1: TOMORROW
Bring in your favorite piece of art, or
any art piece that speaks to you. It can
be a drawing, a painting, a sculpture,
etc. You may make a photocopy, or
print it from a computer, but you
MUST have a hard copy with you… on
your phone doesn’t count!!!
You will also write a paragraph about
your piece, but we will do that
tomorrow.
PRACTICE:
Work
on homework
Work on extra credit (optional) –
if you want extra credit, the work
must be submitted by the end of
class
Begin thinking about your art
piece – feel free to look through
your history or English textbook
once you have finished your
work.