Doppler Effect Calculator
Observed frequency shift from relative motion.
Enter your values
ⓘ Live results
Results
- Observed frequency
- 467.2 Hz
- Frequency shift
- 27.2 Hz
- Percent shift
- 6.2%
Quick answer
Observed frequency = source frequency x (v_sound +/- v_observer) / (v_sound -/+ v_source).
f' = f (v +/- vo)/(v -/+ vs)
How to use the Doppler Effect Calculator
- 1Enter the source frequency and the speed of sound (343 m/s in air at room temperature).
- 2Enter source and observer speeds, positive when moving toward each other.
- 3Read the observed frequency and the amount of shift.
Worked example
Using the values the calculator loads with:
Inputs
- Source frequency440 Hz
- Source speed20 m/s, + toward listener
- Observer speed0 m/s, + toward source
- Speed of sound343 m/s
Results
- Observed frequency467.2 Hz
- Frequency shift27.2 Hz
- Percent shift6.2%
Frequently asked questions
Why does a siren pitch drop as it passes?
As the ambulance moves away, sound waves stretch out, lowering the observed frequency.
Does this work for light?
Light uses a relativistic Doppler formula instead; this tool is for sound waves.
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.