Doppler Effect Calculator
Observed frequency for a moving source.
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ⓘ Live results
Results
- Observed frequency
- 467.24 Hz
- Frequency shift
- 27.24 Hz
- Percentage shift
- 6.19%
- Semitones shift
- 1.04
Quick answer
The Doppler effect raises observed frequency when a source approaches and lowers it as it recedes.
f' = f(v ± vo) ÷ (v ∓ vs)
How to use the Doppler Effect Calculator
- 1Enter the source's true frequency.
- 2Enter source and observer speeds.
- 3Choose whether the source approaches or recedes.
Worked example
Using the values the calculator loads with:
Inputs
- Source frequency440 Hz
- Source speed20 m/s
- Observer speed0 m/s
- Speed of sound343 m/s
- MotionSource approaching
Results
- Observed frequency467.24 Hz
- Frequency shift27.24 Hz
- Percentage shift6.19%
- Semitones shift1.04
Frequently asked questions
Why does a siren drop in pitch?
As it passes, the source switches from approaching to receding.
Does light Doppler shift too?
Yes — that is redshift, though it needs relativistic formulas.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.