The thought that they would have speech in human terms would mean they would have to form their mouths to produce correct sounds, so does this mean we should be able to speak dolphin in the future?
We can only perceive that they communicate with each other as we do.
The world of animal communication is a fascinating subject !
There are many different forms of speech. Remember morse code. One can communicate via short and long signals, be they sound or light or whatever. We need to learn dolphin culture and what matters to them. Then there will be common ground. If we try to speak to them about the NHL it may not register. On the other hand, food, danger and offspring may be common ground for humans and dolphins.
The theme is really interesting, I recently published a post about dogs: https://steemit.com/science/@romel/how-do-dogs-understand-human-speech-actually