Logan
Puritan Board Graduate
This is no more relative than an ambulance pitch changing as it approaches you and then passes you. This is basic wave physics.
There is a difference between speed and frequency.
This is a perceived frequency change (Doppler shift) because of the motion of the ambulance. The sound waves are still traveling at 340 m/s. If you were sitting inside the ambulance you would notice no frequency change because your speed, relative to the ambulance, is zero. Regardless, the speed of the sound is the same.
Einstein himself understood that the experimental evidence of his day showed conclusively that during the part of the year the earth is supposed to be hurling towards a star as it orbits the sun, and six months later is hurling away from the star on the other side of the orbit, we get a zero value for the change in the speed of light. Einstein himself understood that light is a wave and normally you would add the velocity of the earth in one direction and subtract it in the other.
The experiments of Einstein's day could show the earth is at rest under one assumption, it could show the speed of light is a constant under the other. If you're talking about Doppler shift from either moving toward or away from stars, that was not what these experiments were designed to show, yet incidentally, there have been measurements based on the velocity of the earth looking at the Doppler shift of stars. When the Earth's orbit is toward a star we see a tiny rise in the frequency and when it is away from the star we see a tiny lowering of the frequency: consistent with predictions based on Earth's rotational velocity around the sun (which is minuscule compared to the speed of light and requires very sensitive instruments). I cannot think of any geocentric explanation for these Doppler shifts.