# 2D Doppler Shift / Relative Velocities

1. Mar 18, 2013

### awelex

Hi,

I'm trying to adapt the doppler shift formula for a stationary listener and a source traveling in a straight line towards/away from the listener to the case where the source does not move straight towards the listener. For example, suppose that I am looking north and train further in the distance moves from west to east.

The frequency factor in the 1D case is $\frac{v}{v - 333m/s}$. The only thing that changes in the 2D case is that we can't no longer use the absolute velocity v of the source, but have to use the relative velocity with respect to the listener. But this is where I'm stuck: How do I compute this relative velocity when the listener is stationary? Wouldn't that mean that v$_{rel}$ = v$_{abs}$ - 0 = v$_{abs}$? That obviously can't be true.

Thanks,
Alex

2. Mar 19, 2013