( ( (Astounding Sound) ) ) Steven Berger Orefield Middle School 8 th Grade.
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Transcript of ( ( (Astounding Sound) ) ) Steven Berger Orefield Middle School 8 th Grade.
(((((Astounding Sound)(Astounding Sound)))))
Steven Berger
Orefield Middle School
8th Grade
2
Problem StatementProblem Statement
At what column height does sound resonate in a
cylinder of air and water? Will changing the density of a liquid change the speed of sound
through that liquid?
3
HypothesisHypothesis
If the speed of sound in an air and water column can be established by finding its
natural resonance, changing the density of the water (ex. saturating it with salt) will
decrease the speed of sound. According to research, sound travels slower through denser materials because there are more molecules for the sound waves to vibrate.
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ResearchResearch• Sound Wave: A pressure disturbance that travels
by particle-to-particle interaction.
• Frequency: Number of times an object vibrates per second.
• Tuning Fork: A fork shaped acoustic resonator.
• Natural Frequency: When the air column vibrates at the same frequency as the tuning fork.
• Resonance: When an object vibrating at or near the natural frequency of a second object causes it to vibrate.
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Research (cont.)Research (cont.)The tuning fork forces
sound waves into the top of the tube. If the air
column’s natural resonance matches that
of a tuning fork, the sound will get louder and
produce a fundamental.
Add or decrease water in the tube to find the natural resonance of the air column.
Vibration: The complete back and forth motion of an object.
Fundamental: The lowest frequency that an air column will resonate at.
Forced Vibration: When an object forces another into vibration.
For the fundamental, only ¼ of the wavelength goes into the column.
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MaterialsMaterials• set of Tuning Forks/with Striker• plastic tube 5.08cm x 91.44cm• tap water 2L• table salt 340 grams• sugar 340 grams• distilled water 1 ½ L.• magnesium sulfate 453 grams• plexiglass 16 x16 cm thick• gorilla glue• funnel• 4 x 9 x 61 cm wood• 1 x 122 cm flexible tube• masking tape• wood screws
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Procedure for Assembling CylinderProcedure for Assembling Cylinder
1. Cut tube down to 61 cm.2. Drill holes in plexiglass3. Glue 61 cm tube to the
plexiglass base.4. Glue flexible tube to other side
of plexiglass base.5. Put strip of masking tape on
tube and mark off centimeters.6. Attach completed cylinder to
wood base.7. Insert funnel into flexible tube.
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1. Pour the liquid you are going to test into the funnel.2. Add or remove water until the desired air column
height is reached.*3. Strike & hold a tuning fork over the top of the plastic
column.4. Raise or lower the funnel (to change the water
column height) until the sound of the tuning fork becomes the loudest.
5. Record the air column height in cm.6. Repeat the whole procedure again testing different
liquids with different densities.7. Calculate the speed of sound.
Procedure for Testing LiquidsProcedure for Testing Liquids
*most fundamentals occur between 18-33 cm
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Calculating the Speed of SoundCalculating the Speed of Sound The formula for speed of sound is V=4F(L +0.4d)
V is the speed of sound in air column
F is the frequency of tuning fork
L is the length of the air column in meters
D is the diameter of the tube in metersSample Calculation: (D/288 Tuning Fork)
V= 4•288(.28+0.4•.0508)
V=1024(.28+.02032)
V= 1152•.30032
V=345.97 m/s
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Data/GraphsData/Graphs
This graph shows the fundamentals of my control group, tap water. As the tuning fork frequency decreases, the fundamental column height gets
longer. (Note column heights shown are proportionate to actual testing.)
15 16 18.75 21 23.5 25 28 32
0
10
20
30
40
50
60
70
Co
lum
n H
eig
hts
in
CM
C/512 B/480 A/426.6 G/384 F/341.3 E/320 D/288 C/256
Note/Tuning Fork
Fundamentals
water air column
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Data/GraphsData/Graphs
This graph shows the speed of sound for my control group tap water. Most speeds are within 1.5% of the theoretical speed of sound. The researcher multiplied .6 by the temperature and added 331 to find theoretical speed or sound. (V=331+.6T)
Formula for speed of sound: V=4f(L+.4d)
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Data/GraphsData/Graphs
This graph shows the speed of sound for all the liquids categorized by tuning fork and density.
13
ConclusionConclusion• The original hypothesis was incorrect in
thinking that changing the density of water would affect the speed of sound.
• The sound waves that caused a resonance did not go to the bottom of the tube and back. They went to the bottom of the air column and back when the tuning fork goes through one vibration.
• When the frequency of the tuning fork matches the height of the air column the fundamental occurs.
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Conclusion (cont.)Conclusion (cont.)• Benefits: People who design instruments might want to
know the fundamental of a note so they know how to design the instrument. Architects might benefit because they need to know how sound travels in open spaces. Sound waves are also being used to treat people with tremors.
• Areas to Improve:Develop a way to strike the tuning fork the same way for each trial.Be more careful holding the tuning fork in the same place for each trial.
• For further study: To extend this experiment the researcher could try tuning forks with higher and lower frequencies and try other diameter columns.
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Resources/BibliographyResources/Bibliography• Rahn, Joan Elma. "Chapters 1-2." Ears, Hearing & Balance.
New York: Atheneum, 1984. Print.• "Sound." The New Book of Popular Science. Vol. 3. Danbury,
CT: Scholastic Library Pub., 2008. 198-208. Print.• Silver, Jerry. 125 Physics Projects for the Evil Genius, The
Speed of Sound Resonance in a Cylinder, New York: McGraw-Hill, 2009. 188-90. Print.
• "Sound Is a Mechanical Wave." Sound Waves and Music – Lesson 1 The Nature of a Sound Wave. The Physics Classroom. Web. 27 Oct. 2011. <http://www.physicsclassroom.com/Class/sound/u11l1a.cfm>.
• "Resonance." Sound Waves and Music Lesson 5, Musical Instruments The Physics Classroom. Web. 27 Oct. 2011. <http://www.physicsclassroom.com/Class/sound/u11l5a.cfm>.