I have a suggestion, but you might not like it. Get him a little playmate! He'll be so busy playing and having fun he won't bother you anymore.
A female kitten around 4 - 6 months old would be perfect.
Barring that, yes the "startle" method does work too. What I did when I had a cat yowling at my bedroom door was to toss a small paperback book at the door.