# Doppler Shift as Function of MUSIC

1. Oct 30, 2013

### peterblair

Hello, the internet.

I am attempting to graph Doppler Shift as a function of time for a music project. The equation for observed frequency is:

fo=fs(c)/vs(c)

Where
fo is observed frequency
fs is the source frequency
c is the speed of sound
vs is the velocity of the source

But when working with this equation I became confused: The entire point of the Doppler Shift is that the frequency changes over time, but time seems to be represented nowhere in this equation. So, at what point in time, or alternatively how far away from the listener is this equation measuring?

Also, can someone provide me with an equation that could graph fo as a function of time?

Thanks!

2. Oct 30, 2013

### Yanick

The Doppler shift doesn't change with time, it changes with a change in some of the parameters of the equation you have listed.

For example consider a speaker on a moving platform with a stationary observer. As long as the speaker's speed and direction of travel remain constant, the Doppler shift will be constant in time. In other words if you were to plot observed frequency as a function of time it would be a horizontal line crossing the y-axis at whatever observed frequency you measure.

3. Oct 30, 2013

### mikeph

You can graph it if you know v_s. That's where your time dependence is coming from: the moving source.

4. Oct 31, 2013

### dauto

That equation doesn't look right to me. It should be $$f_o=\frac{c+v_o}{c+v_s}f_s,$$ where $v_o$ is the velocity of the observer and the other variables are as defined by the OP.