Sounds like a stimulant to me, not a tic. A stimulant is common in autistic spesctrum disorder. The kids hum or make weird mouth noises or tap or blink or smack their lips, etc. It is comforting in Autism Spectrum Disorders (ASD). MY son used to also suck his shirt from the neck down and make growling noises.
Has he ever seen a neuropsychologist? Who diagnosed him? NEITHER TICS OR STIMS ARE TO GET ON ANYONE'S NERVES. Whew! There 
If he is doing this on purpose, it is neither a tick nor a stimulant. If you feel it's tics, you should take him to a pediatric neurologist to see if he has Tourette's Syndrome, but I'd be careful about thinking he is only doing this to get on your nerves...
My son is almost eighteen and he is MUCH better, but he still has stims. One is he licks the skin around his lips until it is sore and we need to get him a special cream, which he applies. And he sings in his room all the time (he has a very nice voice too!). He has learned how to keep his stims under control in public usually, but is still fidgety when he thinks people are looking at him, like when he had to sing in choir. He would pick at his clothes on stage then look up then look down, you get the picture. He was not trying to misbehave. This is how he deals with stress.
