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DanBM
DanBM
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The Doppler Effect is typically formulated as follows: $$f' = \dfrac{v \pm v_o}{v \mp v_s} \cdot f$$

The reason for the frequency increasing for observer moving towards source seems clear enough. It is because the observer is traveling against the wave motion and so experiences more cycles per second.

On the other hand, if the source is moving, the scenario is very different.

It seems like it might be due to the speed of sound being a constant in the medium (let's say air). The source creates sound by pressurizing and depressurizing the air over and over again. Each pressurization follows upon the next with a frequency equal to $f$. However, sinceLet's assume a spherical sound wave. In the forward direction (the source is also moving intoward the observer), the direction of the propagation of these pressurizations is the same as that of the source's motion. In the backward direction (the source moving away from the observer), the direction of the propagation of these pressurizations is the opposite of that of the source's motion. So the distance (wavelength) between pressurizations is actually greater or less from the standpoint of anthe observer by a factor of $\frac{v}{v \pm v_s}$.

Is that explanation correct?

The Doppler Effect is typically formulated as follows: $$f' = \dfrac{v \pm v_o}{v \mp v_s} \cdot f$$

The reason for the frequency increasing for observer moving towards source seems clear enough. It is because the observer is traveling against the wave motion and so experiences more cycles per second.

On the other hand, if the source is moving, the scenario is very different.

It seems like it might be due to the speed of sound being a constant in the medium (let's say air). The source creates sound by pressurizing and depressurizing the air over and over again. Each pressurization follows upon the next with a frequency equal to $f$. However, since the source is also moving in the direction of the propagation of these pressurizations, the distance (wavelength) between pressurizations is actually less from the standpoint of an observer by a factor of $\frac{v}{v \pm v_s}$.

Is that explanation correct?

The Doppler Effect is typically formulated as follows: $$f' = \dfrac{v \pm v_o}{v \mp v_s} \cdot f$$

The reason for the frequency increasing for observer moving towards source seems clear enough. It is because the observer is traveling against the wave motion and so experiences more cycles per second.

On the other hand, if the source is moving, the scenario is very different.

It seems like it might be due to the speed of sound being a constant in the medium (let's say air). The source creates sound by pressurizing and depressurizing the air over and over again. Each pressurization follows the next with a frequency equal to $f$. Let's assume a spherical sound wave. In the forward direction (the source moving toward the observer), the direction of the propagation of these pressurizations is the same as that of the source's motion. In the backward direction (the source moving away from the observer), the direction of the propagation of these pressurizations is the opposite of that of the source's motion. So the distance (wavelength) between pressurizations is actually greater or less from the standpoint of the observer by a factor of $\frac{v}{v \pm v_s}$.

Is that explanation correct?

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DanBM
DanBM
  • 37
  • 7

Is the Doppler Effect for sound waves with a moving source due to the fact that the wave speed is independent of the source?

The Doppler Effect is typically formulated as follows: $$f' = \dfrac{v \pm v_o}{v \mp v_s} \cdot f$$

The reason for the frequency increasing for observer moving towards source seems clear enough. It is because the observer is traveling against the wave motion and so experiences more cycles per second.

On the other hand, if the source is moving, the scenario is very different.

It seems like it might be due to the speed of sound being a constant in the medium (let's say air). The source creates sound by pressurizing and depressurizing the air over and over again. Each pressurization follows upon the next with a frequency equal to $f$. However, since the source is also moving in the direction of the propagation of these pressurizations, the distance (wavelength) between pressurizations is actually less from the standpoint of an observer by a factor of $\frac{v}{v \pm v_s}$.

Is that explanation correct?