The shift in frequency caused by the Doppler effect is independent...

The apparent frequency $f'$ due to the Doppler effect is given by f' = f \left(\dfrac{v \pm v_o}{v \mp v_s} \right), where $f$ is the original frequency, $v$ is the speed of sound, $v_o$ is the speed of the observer, and $v_s$ is the speed of the source.

The shift in frequency is $\Delta f = f' - f$.

From the formula, it is clear that the shift in frequency depends on the speed of the source, the speed of the observer, and the original frequency of the source.

It does not depend on the separation distance between the source and the observer.