9.5a Doppler effect in sound

Doppler effect

If there is relative motion between a source of waves and an observer of waves then the frequency measured by the observer will be different to that measured at the source or by an observer with no relative motion to the source. This applies to all forms of waves but here we will focus on water waves, sound waves and (in the next subsection) EM waves.

Doppler and sound waves

When dealing with sound waves, you will need to select the most appropriate equation from those provided in the data booklet. Either the moving source equation or the moving observer equation. One the correct equation is chosen it is a case of identifying if the relative motion is bringing source and observer together or further apart, rearranging as required and then solving the equation.

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