my 8 yr old has recently started making odd humming noises. he is unaware he is doing it and his sister has started to take the mickey! he is a bright boy with a real talent for maths, slightly obsessed with numbers, actually, although alsoloves sport, very active. he makes small hums at random times, is he going through a stage/ not the aspergers/autism spectrum ? should i be worried or ignore it? been a few weeks now.