The key thing here is to introduce the vacuum cleaner to him slowly using positive stimuli. This will, in time, turn his foe into a friend.
Switch the vacuum on and instantly give him a treat or a favourite toy, then switch the cleaner off. Repeat a few times and leave it at that. What you are doing here is building an association between the noisy machine and something nice that he loves. In time, both you and he should see this as a fun game and not a scary exercise.