Flash-to-bang Distance

Distance times the gap between a flash you see and the boom you hear. Use Lightning or Fireworks mode. Tap timing stays simple; automatic mode uses the camera and microphone together.

Tap and automatic

Tap mode: tap when you see the flash, tap again when you hear the bang. No camera permission needed. Automatic mode detects a sharp brightness jump and a likely sound onset, then lets you review candidate pairs before saving. Mismatched clocks, a stalled mic, or closing the camera produce no distance.

Air temperature defaults to 20 C and adjusts the speed of sound. Results can show miles or kilometers (with feet or meters too).

Rule of thumb vs the app

A common rule of thumb is about 3 seconds per kilometer or about 5 seconds per mile. That is a rough outdoor approximation. DecibelDock uses the timed delay and temperature-adjusted speed of sound instead of counting seconds in your head — still an estimate, still not a lightning safety tool.

Limits

Thunder is not a point source. Reaction time, reflections, rain and multiple flashes all add uncertainty. Distance does not detect approaching storms or map strike locations. Treat every result as approximate.