The mysterious morse code and headphones in the Battlefield 1 makes the players puzzled with these mysterious objects. Some youtubers and gamers manage to convert morse codes in to readable text, but unfortunately the text codes are also encrypted or in a different orders. If you want to hear and see it yourself, here are some of the location where you can find the headphones and the MCOM machines.
Suez Canal
A (Attack Southern Kantara)
To play these headphones you need find the Mcom machine. Note only one player can hear or play the morse code at a time if lots of player are near the Mcom it will lag and the morse code will not play, to know if someone has headphones and playing on Mcom, you will hear a static hum faint nose. No worries, Mcom machine and headphones is undestroyable it will be there anytime.
If you want to contribute on solving this puzzle there is Google Doc for it (https://docs.google.com/document/d/1L3U-qVHZBOXkvSdiRTar2LtXrDmnluCvXvU0J_k5svs/edit)