免费多普勒频移计算器
计算声源或观测者运动引起的频率偏移。
Observed Frequency
404.6113 Hz
Observed Frequency vs Source Frequency
公式
Doppler Effect for Sound
The Doppler effect shifts the observed frequency when the source or observer is moving relative to the medium.
Formula
f_obs = f_s * (c + v_obs) / (c + v_src)
Sign convention: v_obs is positive when moving toward the source; v_src is positive when moving away from the observer.
计算示例
A 440 Hz siren moves away at 30 m/s, observer stationary.
- 01f_obs = 440 * (343 + 0) / (343 + 30)
- 02f_obs = 440 * 343 / 373
- 03f_obs = 440 * 0.9196
- 04f_obs = 404.6 Hz (lower pitch)
常见问题
Why does an ambulance siren change pitch as it passes?
As it approaches, the sound waves are compressed (higher frequency). As it recedes, the waves are stretched (lower frequency). The transition happens as the vehicle passes.
Does the Doppler effect apply to light?
Yes, but the relativistic Doppler formula differs. For light, there is no medium, and time dilation must be accounted for.
What happens if the source moves faster than sound?
A shock wave (sonic boom) forms. The Doppler formula breaks down and Mach cone analysis is needed.
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