Well, I just don't know what to say. Russian tortoises vocalize a little squeak when they're breeding, but are quiet all the rest of the time. What is happening with him while he's 'meowing'? Is he just sitting there? walking around? trying to eat or drink?
Can you post a picture of your tortoise's habitat for us? and, how long have you had this tortoise?
Dr. Sue Lynch used to be the vet at the Chaffee Zoo. Now she has a mobile vet practice. You can reach her at 559 241-4240. But she only goes to homes in the Fresno/Clovis area.