Calculate the observed frequency of a sound wave when the source or observer is moving. The Doppler effect explains why a siren's pitch changes as it passes by.
Enter your values below
Frequency emitted by the source
Speed of sound in the medium (air: ~343 m/s)
Positive = moving toward observer, negative = moving away
Positive = moving toward source, negative = moving away
How this calculator works
Observed frequency equals source frequency times the ratio of sound speed plus/minus observer speed to sound speed minus/minus source speed. Signs depend on direction of motion.
Common questions about this calculator
These calculators are for educational and informational purposes only. While we strive for accuracy, results should be verified for critical applications. Always consult authoritative sources for engineering or scientific work.
