If you know how to decode the signal further, write in this thread on HN
Zoom uses ultrasonic protocol to detect Zoom sessions nearby. If you are near a conference set, you can check spectrum analyser (e.g. Spectroid for Android) that there is constant signal around 19kHz.
I recorded 74 seconds of such signal from a conference room.
The sequence of actions during the recording was:
- nothing, wait
- 13 sec - click "share screen on laptop", connect
- 30 sec - disconnect
- nothing, wait
- 47 sec - click "share screen on laptop", connect. The room name was "RASMXJ", I don't remember if the previous room had the same name.
- 58 sec - disconnect
- nothing, wait
Spectrogram of the original spikes around 20kHz.
Filtered with high-pass filter and decimeted shows clearly 12 bands spaced by 200Hz.
Spectrograms of the signal, chopped in 5-second intervals is as follows. Each "bit" has ~72ms. The longer dips are connects and disconnects. If Zoom broadcasts the meeting room ID, it must be in the signal before and after the dips.
It seems that around second 8 and second 43 the conferencing set sends the room ID or confirmation code. Confirmation codes in Zoom have 6 letters 6*26=156 states. This can be represented with 156/12=13 12-level "chirps". In the samples I see 9 or 11 and it doesn't seem that there are chirps with two or more different frequencies.
