Doppler Effect Calculator

Model source and observer motion through a medium

The classical Doppler effect changes observed frequency when a source, an observer, or both move relative to the wave medium. This calculator uses positive observer speed toward the source and positive source speed toward the observer. It multiplies emitted frequency by wave speed plus observer speed, then divides by wave speed minus source speed, making approach raise pitch and recession lower it.

With a 440 hertz source, wave speed 343 meters per second, observer approaching at 10 meters per second, and source approaching at 20 meters per second, observed frequency is 480.867 hertz. Enter negative motion values for recession. If source speed approaches the wave speed, the ideal denominator approaches zero and the simple formula ceases to be useful.

Keep the sign convention and regime explicit

The model assumes straight-line motion through a stationary medium and speeds well below the wave speed. It is appropriate for ordinary sound problems, not electromagnetic relativistic Doppler shift or shock-wave behavior at supersonic source speed. All frequency and speed values are handled in your browser. Match every speed to the same reference medium and unit system before interpreting the shift.