http://rockpile.phys.virginia.edu/mod04/mod34.pdf
Paul Fendley: "Now let's see what this does to the frequency of the light. We know that even without special relativity, observers moving at different velocities measure different frequencies. (This is the reason the pitch of an ambulance changes as it passes you it doesn't change if you're on the ambulance). This is called the Doppler shift, and for small relative velocity v it is easy to show that the frequency shifts from f to f(1+v/c) (it goes up heading toward you, down away from you). There are relativistic corrections, but these are negligible here."

That is, if the frequency measured by the stationary observer is f=c/L (L is the wavelength), the frequency measured by an observer moving towards the wave source with speed v is:

f' = f(1+v/c) = (c+v)/L = c'/L

where, for all waves other than light waves, c'=c+v has a definite physical meaning: it is the speed of the waves relative to the moving observer. In Divine Albert's world c'=c+v cannot be the speed of the light waves relative to the moving observer because Divine Albert has said that, for any observer, c'=c is true and c'=c+v false. Yet many Einsteinans suspect that, since the above equations correctly describe the behaviour of all waves (light waves included), c'=c+v may have the same physical meaning in all cases (the case of light waves included).

Pentcho Valev