Signal Sniffer
Listens for machine-readable signals hidden in audio — the kind of thing a Nielsen meter listens for — and decodes whatever it can.
Pick a source. For live listening, hold your phone near the TV/radio speaker.
Audience watermark
Nielsen-style codes hidden at 1–3 kHz
Ultrasonic beacon
Inaudible 17.5–21.5 kHz tones used by tracking & proximity apps
Emergency Alert (SAME)
EAS / NOAA Weather Radio data bursts
Touch-tones (DTMF)
Phone keypad tones
How it works & limits
Audience watermark: Nielsen's meters read codes their encoders hide under the program audio. The exact code format is proprietary and encrypted, so this tool can't read out the station or show ID. Instead it looks for the fingerprint of such a code: several narrow tones in 1–3 kHz that aren't overtones of any music, switching on and off together on a steady clock. Treat it as a strong hint, not proof.
Ultrasonic beacons are decoded fully when they use simple two-tone FSK (bits and any ASCII text are shown). MP3/AAC files usually strip everything above ~16 kHz, so use WAV/FLAC or the live mic. Some phone mics roll off above ~20 kHz.
EAS SAME headers and DTMF digits are public standards and are decoded completely.
If none of these turn up, the verdict is "No fingerprint signal in the stream." The mic needs https or localhost to work; files are analyzed entirely in your browser (first 5 minutes).