Scheduled maintenance tonight at 9:00 PM (HKT). The site may be temporarily unavailable.

Practice & Assess

Doppler Effect

Hear and see how motion affects wave frequency

Live Data

Mach Number (v_s/v)0.07

Observer Position0.0 m

Source Speed (v_s)25 m/s

0Mach 1 ≈ 343 m/s750

Source Frequency (f)880 Hz

Wave Speed in Air (v)343 m/s

343 m/s is the speed of sound in air at about 20 °C.

Observer Position0 m

f^{'} = f (\frac{v}{v \mp v _{s}})

Approaching

949 Hz

Receding

820 Hz

Blue shift: source approaching → observed frequency increases.

Red shift: source receding → observed frequency decreases.

When Mach > 1, the source outruns its own wavefronts (shock wave).