Just for viewing purposes. You can store and calculate this formula only inside the application.
Acoustic Doppler effect
FrObs = FrSource * (PhV + VObs) / (PhV - VSource)
The frequence FrObs which an observer perceives depends on the relative velocity of source and observer as well as of the phase velocity in the medium. The velocities VObs and VSource mean the velocity components that show in direction to each other. So they have to be set positive in case that they show in direction to the other (otherwise their amount has to be set negative).