Perceivable and measurable change in frequency during the propagation of waves caused by the relative motion between the source and observer.
Four different cases must be taken into account for the calculation:
- Source is stationary, observer is moving,
- Observer is stationary, source is moving,
- Source and observer are moving (for the Doppler shift on light waves however the relative motion of the source and the observer in relation to each other is definitive),
- Source is moving at the speed of sound.