Perception of Sound: Bicycle Rider & Car Horn

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When a bicycle rider moves away from a parked car sounding its horn, the rider perceives the sound as having a lower pitch than normal due to the Doppler Effect. As the rider moves away, the sound waves are stretched, increasing the time between wave peaks, which results in a lower frequency perception. The discussion emphasizes understanding sound waves as longitudinal waves, where the distance between waves affects pitch. A visual simulation is recommended to illustrate the Doppler Effect and its impact on sound perception. Overall, the key takeaway is that the pitch of the car horn will appear lower to the cyclist.
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Homework Statement



A person on a bicycle is traveling away from a parked car. If the horn of the car is sounded, how will the bicycle rider perceive the sound?
A)
The pitch will be higher than normal.
B)
The pitch will be lower than normal.
C)
The pitch will appear to steadily increase.
D)
The pitch will appear to steadily decrease.


Homework Equations



none needed



The Attempt at a Solution



i think it may be b but i was hoping to get some guidance, thanks.
 
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You are correct in that the answer is b).
The effect is called the Doppler Effect. Have you studied this?
 
kylepetten said:

Homework Statement



A person on a bicycle is traveling away from a parked car. If the horn of the car is sounded, how will the bicycle rider perceive the sound?
A)
The pitch will be higher than normal.
B)
The pitch will be lower than normal.
C)
The pitch will appear to steadily increase.
D)
The pitch will appear to steadily decrease.


Homework Equations



none needed



The Attempt at a Solution



i think it may be b but i was hoping to get some guidance, thanks.

Think about the sound waves like longitudinal waves, with different concentrated points a certain distance from each other. The distance between these waves is what determines the pitch, closer = higher and farther = lower. Now if these waves are moving toward a person who's moving away from them, there's going to be a little extra time between each concentrated area for them to reach the person, creating the illusion of, like you said a lower pitch than it actually is.

Hope this helps you understand it better. ^-^
 
This link shows a very easy-to-use, visual simulation that shows the Doppler effect:
http://lectureonline.cl.msu.edu/~mmp/applist/doppler/d.htm

click somewhere in the middle of the screen, and a dot will appear. "Sound" waves will begine to be emitted from the dot (it will look like ripples moving out from where rocks have been dropped in a pond). Imagine your bike-rider moving away from the dot. Does the time in between the peaks that reach him increase or decrease? This is the Period, = 1/f. what happens to the period (and to the frequency) if the bike rider moves towards the source?

Now Click-and-hold anywhere on the gray area, then drag your mouse before releasing it. This will cause the 'source' to move as it emits waves. Compare the wavelength (distance between waves) in front of the moving source to the wavelength behind the moving source. Which is bigger? If the wavelength is biggger, what does this tell you about frequency?
 
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