First off, this is not Esbern not having a sound at all. He just responds with those generic greetings and speeches guards give you (even when you have a quest pointing you to talk to him).
I have finished Alduin's Wall and just recruited 3 of my followers into the blades. Delphine tells me ask Esbern about Dragon locations, I ask Esbern. He just says "Good afternoon." or something like that when I dialogue (I believe) should appear.
Previously at the Cornered Rat quest, where I rescue Esbern from the Ratway, he spoke fine and had dialogue.
I'd prefer not to download any mods, if possible.