Random barking: old age or deafness or both?

My old dog has developed a habit of randomly barking; just a single bark followed by a pause, then another bark, pause and a third. Sometimes it is only a single bark, other times more, but three seems to be his favorite pattern.

Many years ago he taught himself to bark when he wanted out; he goes to the back door, barks and waits. It is a similar bark but more whiny, that he is doing now but he may or may not go out if you open the door and the vast majority of the time he is no where near the back door when he barks now.

He does this at irregular intervals and many times it is after he has left the room we are in. At first we thought he was lost but if we ignore him he wanders back in and he will do it standing in the same room with us. Sometimes he will just be laying down behind the sofa and do it. I accuse him of trying to echo locate.

When I put him outside he will stand just outside the door looking into the yard as though he is trying to figure out where he is and why he is out there. Then he will wander off to make his regular circuit. When through he will come stare at the back door from about 10 feet away and start his bark pattern. Often by the time I get to the door he has wandered away again (and waits until I sit down again before coming back and barking).

As I type this he went down the hall, barked three times and then came back and started to lay down at my feet, then, from a half recline, he got up wandered off about four feet and lay down on the floor.

He turned 15 last month, went deaf about two years ago and his eyes are clouding up. Sometimes he acts like he hears something but other times you can stand directly behind him and clap your hands or bang on something and unless you touch him he has no idea you are there.

For those who have had deaf dogs, is this common with them? They can’t hear and assume no one else can or something? Or is the random barking a form of senility?

Anyone got any thoughts or have had similar experiences that might apply?