The document explains the Doppler effect, demonstrating how a sound's frequency appears higher as its source approaches an observer and lower as it moves away. Through various setups involving static and moving observers and sound sources, the experiment measured frequency shifts, affirming that the modeling successfully reflected theoretical predictions. Additionally, it discusses potential improvements for future experiments and suggests further investigation into applications like police radar.

1. Modeling the Doppler Effect
Vijayan Thanasekaran, Ashley
Rodde, Gabriela Quiroz

2. The Doppler Effect: Explained
● As sound source approaches observer, its frequency appears higher
than its actual frequency
○ Each successive wave crest is emitted closer to previous crest
○ Wavelength and frequency are inversely proportional (v = fλ) ->
As wavelength decreases, frequency increases
● As source moves away from the observer, its frequency appears
lower
○ Each successive wave crest is emitted farther from previous

3. Applications of the
Doppler Effect
● Police radar to measure
automobiles speeds
● Doppler radar for storm
systems
● Doppler echocardiogram
to produce images of
heart and calculate
blood flow

4. 1. Can we model the Doppler Effect,
observing higher frequencies of a
sound as it approaches, and lower
frequencies as it moves farther
away?
2. How will our observed values
compare to values calculated using
known equations?

5. Setup
1. Static Observer and Moving
Source
a. Person 1 (observer) on
sidewalk with
microphone
b. Person 2 drives car
(sound source) past
observer at constant
velocity while honking

6. Setup
2. Moving Observer and Static
Source
a. Person 1 (source) in
parked car honking
b. Person 2 drives car past
source at constant
velocity with Person 3
(observer) in passenger
seat holding
microphone

7. Setup
3. Moving Observer and
Moving Source
a. Person 1 drives car
(source) past observer
at constant velocity
while honking
b. Person 2 drives second
car past source at
constant velocity with
Person 3 (observer) in
passenger seat holding
microphone

8. Car honk and background noise has
multiple frequencies.
We chose the dominating frequency of
497 Hz as baseline for stationary car
honk.
Data Extraction

9. Results

10. Set-up 1: Moving Sound Stationary Observer

11. Spectrogram
Passing
observer
Moving towards
observer
Moving away
From observer
Moving Sound and stationary observer

12. Mhz Mhz
Expected 524 Mhz
Observed 522 Mhz
Expected 472 Mhz
Observed 481 Mhz

13. Set-up 2: Moving Observer Stationary Sound

14. Moving towards
Sound source
Passing
Sound source
Moving away from
Sound source
Spectrogram
Moving observer and stationary sound

15. Expected 522 Mhz
Observed 512 Mhz
Expected 471 Mhz
Observed 460 Mhz

16. Set-up 3: Moving Observer and Moving Sound

17. Moving towards
Each other
Moving away from
Each other
Passing
Each other
Spectrogram
Moving observer and moving sound

18. Expected 551 Mhz
Observed 546 Mhz
Expected 447 Mhz
Observed 440 Mhz

19. Discussion

20. Percent Errors:
Calculated

21. Lack of pure tone: +/ - 5 Hz
Speed of vehicle not
constant: +/- 1 m/s
Background noise: +/- 20 Hz
Sources of Error:
Estimated

22. Conclusion
Modeling the doppler effect was successful with our
experiment design. Data reflected the shift in
observed sound frequency for all three scenarios.

23. Improvements ● Pure tone
● Cruise control
● Quieter location
● Video recording to
measure precise time at
which observer and
sound pass each other

24. Further Investigation
● Investigate how police
radar works!
○ Use set up 1
throughout
○ Change speed of car
(moving source) in
each round
○ Calculate the speed
of the car based on
observed frequencies

25. References
By Charly Whisky 18:20, 27 January 2007 (yyy) - Own work, CC BY-SA 3.0,
https://commons.wikimedia.org/w/index.php?curid=1606823
https://science.howstuffworks.com/science-vs-myth/everyday-myths/doppler-effect3.htm
https://www.nssl.noaa.gov/tools/radar/
By Kalumet - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=214411
https://www.thecarconnection.com/news/1094497_uh-oh-police-radar-guns-could-soon-tell-if-youre-texting-too