Board Thread:Writer's Workshop/@comment-26326346-20150422165839/@comment-25226524-20150427145710

"The sounds became more distinguishable as he got nearer to Cell Block D: wails of pain came from the other side of the door."

There does need to be punctuation after "D" because those are two complete sentences. I chose the colon because the second sentence sharpens/further explains the first, but you can use a period if you want. Here is one of the best pages I've found on how to use semi-colons, colons, and dashes.