Doppler Effect Calculator
Compute the observed frequency of a sound wave when the source and/or observer move through a medium. Enter the source frequency, the speed of sound in the medium, the source speed, and the observer speed (each with a toward/away direction) to get the observed frequency, the shift, and the ratio. The calculator flags the supersonic case (source at or above the speed of sound) where a shock wave forms and the simple formula breaks down. Pairs with the Note Frequency and Wavelength calculators for acoustics work. Everything runs locally in your browser.
Result
Classical Doppler effect for sound in a medium: f′ = f · (c + v_o) / (c − v_s), with the sign convention that motion toward the other party is positive — an observer moving toward the source (v_o > 0) raises the pitch, and a source moving toward the observer (v_s > 0) raises it too. If the source moves at or above the speed of sound (v_s ≥ c) the denominator reaches zero or goes negative and a shock wave (sonic boom) forms; the simple formula no longer applies and the calculator reports it. For light in a vacuum this classical formula is only an approximation — use the relativistic Doppler formula for high precision. Everything runs locally — nothing leaves your browser.