SONAR
offYour device, seeing with sound
The speaker sends out a tone too high for you to hear, and the microphone listens to its echoes. Anything that moves changes the echo: your hand in the air, someone walking in, your chest as you breathe. Turn the volume up (no headphones), give the microphone permission, and keep still for about ten seconds while it finds the best inaudible tone for your speaker.
Finding the tone
Trying high tones one by one…
Wave at it
Hold a hand 10 to 40 cm from the device. Push it toward the screen, pull it back, or wave. The orb follows your hand; below, every movement leaves a streak in the echo.
The echo
Each row is a moment, newest at the top. The bright line in the middle is the tone itself; streaks to the right are things coming closer, to the left things moving away.
Breathing, from a distance
Put the device on a table 30 to 60 cm from your chest, screen toward you, and sit still. Every breath moves your chest a few millimetres, which turns the echo by a measurable amount. Give it about 30 seconds.
Is anyone moving?
Leave the device in a room. It hears movement anywhere in front of it, a few metres away, with no camera: the timeline shows the last two minutes.
Everything happens in this page: no sound is recorded or sent anywhere. Some speakers and microphones barely reach these frequencies; if the tone search finds nothing, try another device.