A note on moving multipole sources of sound

The object of this note is to draw attention to the need, when speaking of a moving multipole source of sound, to state whether it is based on the wave equation for the velocity potential or the wave equation for the perturbation pressure. The theory of moving multipole sources of sound is firmly established, but, owing to lack of precision, some seemingly contradictory results are to be found in the literature. The reasons for these seemingly contradictory results are examined, and various basic relationships between a moving multipole sound field and its method of generation are established.