An acoustic space-time and the Lorentz transformation in aeroacoustics
  In this paper we introduce concepts from relativity and geometric algebra to aeroacoustics. We do this using an acoustic space-time transformation within the framework of sound propagation in uniform flows. By using Geometric Algebra we are able to provide a simple geometric interpretation to the space-time transformation, and are able to give neat and lucid derivations of the free-field Green's function for the convected wave equation and the Doppler shift for a stationary observer and a source in uniform rectilinear motion in a uniform flow. 
Alastair Logan Gregory, Samuel Sinayoko, Anurag Agarwal, Joan Lasenby
physics.flu-dyn