Cats and dogs have a certain vocabulary. I surveyed my cats and they don't meow for everything. They make other sounds that I'm not able to reproduce. The meow may be on different tone depending on what they want. For the dogs, it's the same. Plus, if a dog makes some noise, the others follow him quickly.
I cannot pronouce myself for cimps, either.
My point is, other animals than dolphins are able to speak.