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The source audio file you produce will be a mix of 5 DTMF dual tones. Played at the same time.
There are 5 layers in the mix. Each layer will use a different set of DTMF dual tones to represent the digits 0-9
The audio track will then be mixed with music and played over a loud speaker.
All DTMF dual tones will be in the frequency range 17,000 to 18,500 Hz.
It is critical you can not hear the DTMF dual tones which is why we use high frequencies.
1) Identify the best frequencies to ensure no clash from harmonics etc.
2) Create test source audio
3) Mix with music
4) Play it through a loud speaker
5) Build a recording app to record the complete audio content of the room through the mobile devices microphone.
6) Process the audio and accurately extract the 5 sets of DTMF tones on the recording.
7) Allocate each DTMF dual tone to its corresponding layer and digit (0-9)
e.g. Layer 3, Digit 4 means the 3rd digit (out of 5) is a 4.
8) Display the correct 5 digit code.
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