Losing the ability to speak

I had a very hard time trying to understand my Dad yesterday.  He kept talking and my mom wasn't there to interpret, so I have no idea what he was talking about.  When he got mad at my son though, I could understand him just fine!  I'm worried about further down the road.  He knew sign language, but that's not much help.  I bought my son a record a book this week and I'm hoping that one of his better days, they can record him.  I know my kids love their Papaw!  It's progressing so fast!  My family ordered a communication device.  I have no idea how it works, but I'm hopeful!