Find the heard frequency f′ = f (v + vo) / (v − vs) for one-dimensional sound in still air.
| Heard f (Hz) | – |
Use this calculator for the classic 1D Doppler shift. v is the speed of sound. Observer speed vo is positive if the observer moves toward the source; source speed vs is positive if the source moves toward the observer. A siren coming at you raises the pitch; receding lowers it.
A 440 Hz source, 343 m/s sound, vs = 0 and vo = 20 m/s toward the source gives about 466 Hz. Source speed cannot equal sound speed (that would zero the denominator). This is still air in one dimension, not a windy 3D field and not the electromagnetic Doppler formula.
Source f (Hz): Frequency at the source, in hertz.
Sound speed (m/s): About 343 m/s in air at 20 °C.
Source speed (m/s): Positive toward the observer.
Observer speed (m/s): Positive toward the source.
Heard f (Hz): Observed frequency f′.
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