ACOUSTIC SENTRY

MICROPHONE LISTENING POST · RUNS ONLY ON THIS DEVICE · NOTHING IS RECORDED OR SENT

STOPPEDPress START and allow the microphone.

LIVE SOUND

LEVEL—

STEADY ENGINE TONE—

HELD FOR—

TREND—

SPECTRUM 0 – 1500 HZ · RED MARKS = ENGINE HARMONICS BEING TRACKED

ENGINE SENSITIVITY MEDIUM ALARM AFTER STEADY TONE FOR 6 s BLAST TRIGGER (JUMP ABOVE BACKGROUND) 22 dB

IGNORED TONESNONE

Experimental. It has only been tested with artificial sounds, never with a real attack drone.
It listens for a steady engine drone (propeller drones with piston engines sound like a moped that never changes gear) and for sudden loud blasts.
It cannot hear missiles or jet-powered drones coming — they arrive faster than or as fast as their sound. It also misses quiet electric drones.
Range is short: roughly as far as you could hear the engine yourself. Outdoors on a roof, away from traffic, is far better than indoors.
Generators, trucks idling and pumps cause false alarms. Start it while they are running (it learns the background for 15 seconds) or press IGNORE THIS SOUND.
Silence does not mean safe. Use it as one more pair of ears, especially while you sleep, never as your only warning.
Keep the device plugged in, volume at maximum, and this page open on screen.