I searched the modem chips but i think it is not the solution for me.
If i understood modem chips' operation correctly,
they can do much more complicated operations than just sending data over sound.
What i wanna do is:
For example;
on one hand, i have a message board, maybe graphical,
i will send some text or graphics to it,
this message could be as high as 128 kbytes,
on the other hand, i have a device that can play sound,
this sound could come from a cellphone music player, a mp3 player, even call from an another cellphone, radio receiver, etc.
Finally, with playing sound i could send data to my message board.
Message board will be made by me,
sound that need to be played will be generated by me.
If there is some other cheap methods for data over voice, i wanna learn.
If it would be a solution for some methods, i can program and use mcu.