How does a moving sound source physically compress the waves emitted in front of it and lengthen the waves emitted behind it? Virtually all descriptions of the doppler effect provide nice visuals of waves bunched up in front of a moving source and spread out behind such a source. However, I would like a detailed description of how a moving source engages with the medium through which it travels to accomplish this. For example, does the bulk modulus of the medium change by virtue of a source moving through it? If so, does that factor into the frequency perceived by the listener?
