I think lots of children do similar with visual things ie focus on a detail not the full picture eg focus on the wheel of the car spinning not the whole car. I think its more common in ASD not to be able to filter out the different noises so you can hear everything super loud but can't decide which noise is the most important. My son doesn't react to noises much but if a plane goes over or he hears music he covers his eyes. I think this is mono channel or something - shutting off one sense to concentrate on another or to stop overload eg he can't cope with a lot of auditory info and visual info at same time. Not really figured it out but hopefully he will be able to tell me one day.