King Nebuchadnezzar of Babylon was trying to build an empire. Defeating several small enemies one by one was going to be much easier for him than fighting a group of enemies who had banded together to fight a common enemy. The nations around Israel knew this and were doing their best to fight King Nebuchadnezzar together. They sent envoys to Jerusalem to meet together and arrange joint resistance.
But it wasn’t going to work.
While the envoys were there, God told Jeremiah to make a yoke and wear it to act out a message for the foreign kings whose envoys had gone to Jerusalem (Jeremiah 27:1-11).
The message was for the kings of Edom, Moab, the sons of Ammon, Tyre, and Sidon, telling them that they would all have to serve the king of Babylon. Jeremiah was to enact the parable by wearing the yoke and verbally deliver the message to the envoys who had come to Jerusalem.
How easy would Jeremiah have found it to communicate with these foreign envoys? Please note that the following information is gleaned from various places on the internet. I do not have any personal knowledge of any of these languages!
The Edomite language was very similar to Hebrew, but probably written with a Phoenician script. Now considered to be a dialect of Hebrew (see https://en.wikipedia.org/wiki/Edomite_language).
The Moabite language was also very similar to Hebrew but probably written with a Phoenician script. Now considered to be a dialect of Hebrew (see https://en.wikipedia.org/wiki/Moabite_language).
The Ammonite language was also very similar to Hebrew and used the Hebrew script. Not considered to be a distinct language from Hebrew (see https://en.wikipedia.org/wiki/Ammonite_language).
The people of Tyre and Sidon would both have spoken the Phoenician language, which was very close to Hebrew in both grammar and vocabulary (see https://en.wikipedia.org/wiki/Phoenician_language).
All of these languages or dialects were very close to Biblical Hebrew, but would have required some knowledge of the differences in order to make communication easy. Some of the differences are features that make these languages more similar to Aramaic (the language that the Babylonians spoke). Overall, if Jeremiah had to communicate with people who spoke the surrounding languages, he would have needed to understand greater differences than just accents, but not as great as the differences between English and any other language. For many of the local languages, the differences may have been just a little bit more than the differences between Australian English and American or Indian English. Comprehension between the languages is apparently easy, but some confusion may arise at times.
The yoke was a strong visual message of servitude. It could communicate without words, and would be remembered by the envoys even if verbal communication failed.