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Calculations Involving the Doppler Effect
Velocity of sound relative to air = v
Frequency of emitted sound = f
Apparent frequency of received sound = f’.
Moving Source (stationary observer)
If the source moves with a velocity of magnitude vs (relative to the air) then the velocity of the waves relative to the source is (v±vs).
so in this case,
The apparent frequency of the sound, f’, as measured by the observer, will be equal to v/.
Therefore, the apparent frequency is given by