fire a chirp from your speakers · microphone catches the echo · estimate distance to the nearest surface · echolocation in a browser · runs locally
how it works
plays a 20 ms frequency sweep (1500–4200 hz) through your speakers and records the microphone simultaneously. echoes from walls, furniture, and nearby surfaces arrive milliseconds later. round-trip delay → distance: 1 ms ≈ 34.3 cm (sound travels at 343 m/s). point toward a wall and try different distances.
✦ quiet room · volume above 60% · echo cancellation is disabled by this tool
ping
why this matters
- any page with mic permission can range surfaces. this exact technique is used in retail analytics SDKs and acoustic positioning systems to infer room layout and device placement without GPS or WiFi.
- chirp vs click. a linear chirp (frequency sweep) gives better noise rejection than an impulse. the matched-filter response is a tight correlation peak that survives reverberant rooms where a simple click would smear.
- echo cancellation exists for this reason. aec (acoustic echo cancellation) was originally designed for telephony but also suppresses this cross-coupling. disabling it — as microphone-abusing apps often do — unmasks the echo signal.
- best results. aim the laptop at a hard flat wall within 1–2 m, crank volume, and fire multiple pings. the direct path (speaker→mic, ~0.6 ms) is filtered out automatically.