Doppler EK 749.

[GRod18]

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If the source of a sound wave and the observer are stationary, and there is a steady wind blowing from the observer to the source, how will the doppler effect change the observed frequency?

Answer there will be no doppler effect.

The main question I have is why does the wind create extra velocity to the observer and stationary object, both equal and opposite the wind? Is this because of newton's 3rd law? Dosen't seem too intuitive to me, and EK dosen't really explain it.

I always thought that doppler effect was a strong point of mine zzz lol..

 

[Rabolisk]

Can you clarify what you mean by "extra velocity"? The doppler effect doesn't occur because there is no relative velocity between the objects. Regardless of how far apart they are, what medium the sound travels through, or any other factors, doppler effect is only observed when one's displacement relative to the other is changing.

 

[GRod18]

ok well this is what EK said.

I just haven't seen a question presented in this manner in other review texts.

The wind is equivalent to giving both the source and the receiver a velocity equal in magnitude and in the opposite direction to the wind. Their relative velocity remains the same. in this case, the relative velocity is zero, and there is no Doppler effect.

 

[Rabolisk]

OK, so I believe I understand what you're saying. The velocity of the objects must be relative to some frame of reference. In this case, that is air since sound travels through air. When wind blows, air travels relative to the source and the observer. Put another way, the source and the observer move relative to the air. Hence both vs and vo increase to the direction opposite the direction the wind blows towards.

Mathematically you can see that this would only affect doppler effect if there was some net movement between the source and the observer to begin with.

 

[GRod18]

ah ic, ok just a lame explanation on EKs part I guess, in so many. Good thing I'm pretty much finished with it lol.. and then just 10 more days of various other passages