No, that is how humans hear Pokemon.
Pokemon speak a special Poketalk that only they truly understand. You're playing as a pokemon in PMD, therefore, you are able to communicate with other pokemon the way humans communicate with other humans. Basically, the Pokemon are all actually speaking Poketalk, but because it's a game, their conversations are presented in human language. That way, the player knows what's going on, and they can interact with the other characters.