Use audio as QR code alternative for getting UUID

[adibzter]

Implementation

1. Change UUID into a form of audio.
2. Device A listens to surrounding audio from the mic.
3. Device B plays audio of the UUID.
4. Device A decode the audio into UUID and send data to the server.

The frequency will start from 4000Hz with increments of 50Hz.

let code = {
  '0': 4000,
  '1': 4050,
  '2': 4100,
  ...
};