The full acoustic spectrum of your environment — from infrasound rumble to near-ultrasonic.
Mains hum at 50 or 60Hz. HVAC resonance. The unique acoustic fingerprint of every room.
Sounds you cannot hear but your phone already captures.
your room has a unique acoustic signature.
Reflection patterns, resonant frequencies, background hum —
combined, they can identify a specific room with >90% accuracy.
Advertisers have used ultrasonic beacons embedded in TV ads
to detect which room you're in across multiple devices simultaneously.
range:
—peak freq
—peak dB
—noise floor
waiting for microphone
0 Hz—22 kHz
tap the spectrum to inspect a frequency
waterfall — time → · freq ↑
detected peaks
start microphone to detect peaks
▶ how does this work?
The Web Audio API feeds your microphone through an AnalyserNode running a
Fast Fourier Transform (FFT). This converts the time-domain audio signal into frequency bins —
each bin shows how much energy exists at a specific frequency.
With an FFT size of 4096 and 44.1kHz sample rate, each bin covers ~10.8Hz.
The waterfall scrolls left-to-right: time progresses rightward, frequency increases upward, so you can see how the spectrum evolves.
Peaks are detected when a bin exceeds the noise floor by >15 dB.
Known signatures: 50Hz = European mains · 60Hz = North American mains ·
100/120Hz = LED flicker harmonic · 18–22kHz = ultrasonic beacon or pest repeller.