Reducing Sound Intensity of an
Aerodynamic Vehicle
Ryan Gohlke – SHHS
Alex Henry – WMHS
Wouldn’t It be Great for a Car
Gohlke-Henry
2
Background
• Old Time vents (1950s)
– Produced more drag =
more $
– No vents on modern
cars
– Vortices shedding
around window posts
http://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/1965_AMC_Ambassador_detail_
of_vent_window.jpg/330px-1965_AMC_Ambassador_detail_of_vent_window.jpg
Gohlke-Henry
3
Applications
• Automotive design
• Engineering
• Everyday drivers
Gohlke-Henry
4
Purpose
• To reduce sound intensity in a vehicle driving
at high velocities while keeping drag force
consistent
Gohlke-Henry
5
Aerodynamics
• Drag
• Lift
http://www.motiva.fi/myllarin_tuulivoima/windpower%20web/en/tour/wtrb/aeroforc.htm
Gohlke-Henry
6
Open and Closed Pipe Resonance
• Resonance
• Speed of sound = 343 m/s
± depending on temperature
http://hyperphysics.phy-astr.gsu.edu/hbase/waves/imgwav/ccyl.gif
Gohlke-Henry
7
Node and Antinode
• Standing wave
• Node – resting point
• Antinode – farthest
displaced point
http://www.antonine-education.co.uk/Image_library/Physics_2/Waves/Superposition/wav_26.gif
Gohlke-Henry
8
Interference
• Intersecting points
create beats
• Beats = thump
Gohlke-Henry
9
Damping
• Displace wave
molecules to assure
standing wave is harder
to form
http://www.splung.com/kinematics/images/damped_oscillations/damped_oscillations.gif
Gohlke-Henry
10
Invention…Is Conceived!
Gohlke-Henry
11
Invention is Officially Born
Gohlke-Henry
12
Deresonator
• Printed at different
angles to destruct the
formation of standing
waves
Gohlke-Henry
13
Hypothesis
• If the deresonator is manufactured at 45°,
then intensity will decrease and drag force will
remain the same as if the windows were not
open.
Gohlke-Henry
14
PROCEDURES
Gohlke-Henry
15
Sound Intensity
Materials
Air Supply Model SF-9216
Logger Pro
Vernier Microphone
Round Bottom Flask
Gohlke-Henry
17
Procedure
Gohlke-Henry
18
Take the Maximum!
Gohlke-Henry
19
Data
Sound Intensity
16
Trials No Angle 30º
45º
60º
17
1
3.563 2.807 2.890 2.761
18
2
3.596 2.795 2.787 2.783
19
3
3.618 2.846 2.799 2.756
20
4
3.606 2.797 2.800 2.767
21
5
3.581 2.803 2.779 2.767
22
6
3.586 2.821 2.865 2.762
23
7
3.505 2.785 2.787 2.757
8
3.535 2.818 2.792 2.744
24
gap between numbers
9
3.517 2.781Significant
2.840 2.753
25
10
3.586 2.812 2.829 2.734
26
11
3.607 2.845 2.785 2.767
27
12
3.642 2.817 2.812 2.769
28
13
3.547 2.785 2.843 2.744
29
14
3.534 2.793 2.818 2.752
30
15
3.557 2.804 2.807 2.745
Gohlke-Henry
3.573 2.852 2.841 2.773
3.597 2.834 2.863 2.773
3.558 2.804 2.831 2.738
3.580 2.821 2.840 2.762
3.540 2.840 2.846 2.773
3.543 2.831 2.811 2.757
3.597 2.812 2.830 2.746
3.583 2.837 2.835 2.762
3.617 2.780 2.857 2.742
3.614 2.810 2.846 2.766
3.579 2.803 2.820 2.752
3.579 2.797 2.804 2.743
3.549 2.802 2.807 2.759
3.590 2.801 2.809 2.781
3.623 2.818 2.843 2.756
20
Observations
Observations
Trial
Sound Intensity Observations:
Used duct tape to secure flask, will do so from
now on
De-resonator was not fully secured and fell into
flask
De-resonator was not fully secured and fell into
flask
De-resonator was not fully secured and fell into
flask
Gohlke-Henry
No Angle:
Trial 7
30°: Trial
15
30°: Trial
22
60°: Trial 3
21
Analysis
• H0: µno angle = µ30° =µ45° =µ60°
• Ha: Not all µno angle, µ30°, µ45°, µ60° are equal
• Most assumptions are met for Sound Intensity
– S.R.S., Distribution normal by C.L.T.
– Deviation Rule of Thumb is not met
Gohlke-Henry
22
Intensity Box Plots
Sound Intensity (dB)
Gohlke-Henry
23
Possible Overlap
Sound Intensity (dB)
Gohlke-Henry
24
Intensity Stats
Sound Intensity (dB)
x̄i
Sxi
ni
No Angle
3.577
0.03315
30
30°
2.812
0.01986
30
45°
2.823
0.02719
30
60°
2.758
0.01257
30
Gohlke-Henry
25
ANOVA Test Results
• Reject H0
• p-value of 0.0000 is less
than the alpha level of 0.05
• Means are different and
sound intensity has
decreased
• There is a 0% chance of
getting results this extreme
based on chance alone
assuming H0is true
• Standard deviation rule of
thumb not met
Gohlke-Henry
26
Overlap Results
•
•
•
•
•
H0: µ30° = µ45°
Ha: µ30° ≠ µ45°
Assumptions met
Fail to reject H0
The two deresonators
could produce a sound
intensity at the same level
• 5.39% chance of getting
results this extreme
based on chance alone
assuming H0 is true
Gohlke-Henry
27
Drag Force
Materials
Round Bottom Flask
Light String
Frictionless Pulley
Vernier Dual Range
Force Sensor
Gohlke-Henry
29
Procedure
Gohlke-Henry
30
Take the Mean!
Gohlke-Henry
31
Data
14
15
30º
45º
60º
16
0.054 0.052 0.048
17
0.053 0.049 0.048
18
0.056 0.049 0.052
19
0.055 0.053 0.045
20
0.057 0.054 0.051
21
22
0.054 0.054 0.050
23
0.054 0.050 0.055
Insignificant gap between numbers
24
0.055 0.047 0.052
25
0.055 0.048 0.053
26
0.056 0.051 0.053
27
0.056 0.048 0.052
28
0.053 0.051 0.055
29
0.058 0.052 0.053
30
Drag Force (N)
Trials No Angle
1
0.045
2
0.048
3
0.051
4
0.047
5
0.049
6
0.048
7
0.050
8
0.050
9
0.048
10
0.049
11
0.049
12
0.046
13
0.050
Gohlke-Henry
0.050
0.049
0.047
0.046
0.050
0.052
0.049
0.048
0.049
0.049
0.051
0.050
0.048
0.050
0.051
0.050
0.040
0.055
0.059
0.059
0.055
0.059
0.056
0.057
0.057
0.057
0.056
0.060
0.061
0.059
0.058
0.055
0.061
0.059
0.050
0.051
0.052
0.051
0.051
0.052
0.051
0.049
0.052
0.051
0.051
0.051
0.052
0.050
0.050
0.051
0.053
0.056
0.053
0.054
0.055
0.053
0.058
0.057
0.054
0.056
0.054
0.056
0.056
0.057
0.055
0.057
0.055
0.056
32
Observations
Observations
Trial
Drag Force Observations:
Force Sensor was moved during trial, experiment
was reset
LabQuest recorded inaccurate data, flask was repositioned
LabQuest recorded inaccurate data, flask was repositioned
LabQuest recorded inaccurate data, flask was repositioned
Gohlke-Henry
45°: Trial 22
30°: Trial 9
No Angle: Trial
26
60°: Trial 17
33
Analysis
• H0: µno angle = µ30° =µ45° =µ60°
• Ha: Not all µno angle, µ30°, µ45°, µ60° are equal
• Assumptions are met for drag force
– S.R.S., Deviation Rule of Thumb, Distribution
normal by C.L.T.
Gohlke-Henry
34
Drag Force Box Plots
Drag Force (N)
Gohlke-Henry
35
Possible Overlap
Drag Force (N)
Gohlke-Henry
36
Drag Force Stats
x̄i
Sxi
No Angle
0.049
0.00230
30
30°
0.057
0.00225
30
45°
0.051
0.00168
30
60°
0.054
0.00299
30
Drag Force (N)
Gohlke-Henry
ni
37
Drag Force Test Results
• Reject H0
• p-value of 0.0000 is less
than the alpha level of
0.05
• Means are different and
drag force has varied in
the positive direction
• There is a 0% chance of
getting results this
extreme based on chance
alone assuming H0 is true
Gohlke-Henry
38
Overlap Results
•
•
•
•
•
H0: µ30° = µ60°
Ha: µ30° ≠ µ60°
Assumptions met
Reject H0
The two deresonators
cannot have the same
drag force
• 0.01% chance of getting
results this extreme
based on chance alone
assuming H0 is true
Gohlke-Henry
39
Conclusion
• Sound Intensity
• Drag Force
– 60° followed by 30°,
then 45°
– 45° followed by 60°,
then 30°
Overall hypothesis was rejected
60° was deemed
Gohlke-Henry
40
Force Diagram
Lift
Drag
Gohlke-Henry
41
Further Research
• Varying wind velocities and shape
• Full-scale testing, apply fit deresonator to
window of a car
Gohlke-Henry
42
Acknowledgements
• Chris Oesterling
• Thomas J. Benson
– Printed deresonators
– Mentor
Gohlke-Henry
43
Works Cited
Aerodynamic Forces: Definitions of Lift and Drag. Digital image. n.p., n.d. Web. 03 Nov. 2014.
<http://www.motiva.fi/myllarin_tuulivoima/windpower web/en/tour/wtrb/aeroforc.htm>.
Aerodynamic Forces: Definitions of Lift and Drag." WindPower. Danish Wind Industry Association,
29 Sept. 2002. Web. 17 Sept. 2014.
<http://www.motiva.fi/myllarin_tuulivoima/windpower%20web/en/tour/wtrb/aeroforc.htm
>.
Benson, Tom. "What Is Drag?" National Aeronautics and Space Administration.NASA. gov., 16 July
2014. Web. 17 Sept. 2014. <http://www.grc.nasa.gov/WWW/k-12/airplane/drag1.html>.
Buscarello, Ralph T. "Mechanical Resonance - Detuning Resonant Part versus Reducing Vibration
at the Source." Update International, 2013. Web. 22 Sept. 2014. <http://www.updateintl.com/VibrationBook2i.htm>.
Closed-End Resonance. Digital image. Resonance. n.p., n.d. Web. 22 Sept. 2014.
<http://www.physicsclassroom.com/Class/sound/u11l4b4.gif>.
"Damped Oscillations." Physics Online, Physics Help, Physics Course. N.p., 07 June 2008. Web. 02
Dec. 2014.
"Damping, Natural Frequency and Resonance." Simple Harmonic Motion and Damping Revision.Scool, 7 May 2014.Web. 18 Sept. 2014. <http://www.s-cool.co.uk/a-level/physics/simpleharmonic-motion-and-damping/revise-it/damping-natural-frequency-and-resonance>.
George, Patrick E. "How Aerodynamics Work" HowStuffWorks.InfoSpace LLC, 17 Mar. 2009. Web.
18 Sept. 2014. <http://auto.howstuffworks.com/fuel-efficiency/fueleconomy/aerodynamics.htm>.
Henderson, Tom. "Closed-End Air Columns." Closed-End Air Columns. n.p., 22 Sept. 2014. Web. 23
Sept. 2014. <http://www.physicsclassroom.com/class/sound/Lesson-5/Closed-End-AirGohlke-Henry
44
Columns>.