Doppler vehicle speed

Doppler listens for a pitch drop as a vehicle passes a stationary phone and turns that into a rough speed estimate. It is educational, not radar.

Live estimate and final result

While recording, the gauge can show a provisional speed labelled LIVE · ESTIMATING once an approach pitch starts to drop. That live number is smoothed and is not saved. When the pass ends, a stricter final analysis replaces it. Only an accepted final speed goes into history.

If the pass cannot support a speed — silence, a flat tone, heavy clipping, or no clear before/after drop — DecibelDock shows a written reason instead of inventing a number.

Continuous mode

An optional Continuous switch (off by default) keeps listening after each accepted pass, shows the last finished speed as "Last pass," and resets for the next vehicle. Each accepted pass is saved with its time. One preview use is spent per Doppler session, not per car. Stop, or leaving the tool, ends capture. There is no background Doppler microphone.

Limits you should know

Geometry usually makes the estimate a little low. Broadband engine and tire noise can be hard to track. Overloaded frames are left out of the analysis. Doppler is approximate and depends on your phone. It is not for traffic enforcement or safety decisions.