House training for the silent type

Question
Hello. I have a 3.5 mo. old male GSD.
He is smart, funny and ready for antything.
He learns quick and follows some of the rules most of the time.

However, he is silent.
He rarely barks, growls, makes any sound, even while playing.
So, when he needs to go outside...he 'asks' by basically just walking to the door.
It doesn't work out well if I am in the other room.
I try to keep on his heels, but I do like to let him explore.
I keep an eye out for him. I have tried (when he goes to the door) to insight him to bark or even whine. Nothing.

This has resulted in quite a few accidents which were my fault for not paying close enough attention.

But, what, if any, advice could you ffer me to bring out the 'verbal beast' in the strong/silent type?

He is a very good boy...I just need to get him to speak up.

:) Thanks!!!!!!!!!!!!!!!!!!!!!!!

Answer
Some people hang a bell on the door.  Your lucky, with the Christmas decor already in the stores they should be cheap and easy to find now.  Hang it low on the side that opens.  Lead him to it and lift his paw to hit it.  Often dogs paw the door even without a bell, so he should quickly catch on.  As soon as you hear the bell, tell him ''Good dog!'' and hustle to open the door for him.