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MotionLab
Why an ambulance siren sounds higher-pitched approaching and lower-pitched leaving.
As a sound source approaches, each successive sound wave is emitted from a closer position, compressing the wavelength and raising the perceived frequency (pitch) — moving away does the opposite, stretching wavelength and lowering pitch.
This computes the case of a moving source and stationary observer — a moving observer, a moving medium (wind), or both source and observer moving simultaneously all have their own variations of the full Doppler formula.
Observed frequency (Hz)
482.173
For a source approaching a stationary observer: f' = f·v / (v − vₛ)
What you entered
f' = f × v ÷ (v − vₛ)
440 × 343 ÷ (343 − 30)= 482.1725 HzResult
Observed frequency (Hz): 482.173
A 440 Hz source approaching at 30 m/s sounds like 482.17 Hz to a stationary observer.