When Louis and his father talk about fact that Louis has no voice the cob calls Louis dumb what dose the cob mean by dumb

when the cob calls louis dumb he isn't saying that he is stupid or not intellagent, he is saying that louis cant talk. if you read after when the cob says dumb the book says that the cob saw louis look sad, so he explained to him that dumb has multiple meanings and one of them is not being able to talk, like deaf and blind.