The document describes the doppler-ganger game, where players analyze visual scenarios involving sound frequency perception due to the Doppler effect. It presents various situations with stationary and moving cars, detailing how frequency is perceived by different observers. Explanations clarify the impact of motion and temperature on sound waves and frequency perception.

1. Doppler-ganger Game
doppelgänger: an apparition or double on a living
person.
To play the Doppler-ganger Game you must describe the visual
scenario of a doppler effect situation into English. In the end
there will be two versions (visual and written) of the same
doppler situation.

2. 1) The car is parked and
Person 1 and Person
two are sitting on the
sidewalk. The car horn
goes off.
What frequency does
Person 1 hear the horn
compared to Person 2?
1. P1 < P2
2. P1 = P2
3. P1 > P2
4. No way to know
Person 1
Stationary
Person 2
Stationary
Car
Stationary

3. 2) The car is driving and
Person 1 and Person
two are sitting on the
sidewalk. The car horn
goes continuously
sounds.
What frequency does
Person 1 hear the horn
compared to Person 2?
1. P1 < P2
2. P1 = P2
3. P1 > P2
4. No way to know
Person 1
Stationary
Person 2
Stationary
Car
Driving

4. 3) The car is parked and
Person 1 and Person
two are sitting on the
sidewalk. The car horn
goes off.
What frequency does
Person 1 hear the horn
compared to the kids
1. P1 < P2
2. P1 = P2
3. P1 > P2
4. No way to know
Person 1
Stationary
P2
Stationary
Car
Stationary

5. 4) The air temperature
increases by 10o
C on the
second story. Describe
the sound differences due
to this temperature
difference.
____________________
____________________
____________________
____________________
____________________
____________________
Person 1
Stationary
Person 2
Stationary
Car
Driving

6. Explanations
1. P1 = P2. The car is not moving and neither are the people. This means
that when the two people will hear the same frequency because there is no
compression.
2. P1 > P2. The car is moving towards P1 and away from P2. This means
that P1 is hearing compressed waves, increasing the perceived frequency
of the car horn. P2’s waves are now even less frequent than in Q1
because the waves are “driving away” from them.
3. P1 = P2. P2 on skates and P1 sitting hear the same frequency because
the waves aren’t moving at a different compression. P2 is just moving.
4. When there is a great temperature gradient, waves refract down towards
the cooler air and greatly increase the range of the sound.