this is a solution for transmitting data over audio. like dial-up modems.
methods like FSK, ASK and PSK are going to be used for modulation.
for more knowledge see this link of wikipedia
in the transmitter side, using ask.py you can modulate a data into audio.
and then in the receiver side, you can demodulate audio using de-ask.py
demodulation is done by getting mean value of absolute value of a set of samples
and then comparing it with a normalized value.
also a synchronization method is needed for this algorithm (TODO).