Wonder Why Chuggington?

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I wonder why the Chuggington engines are so noisy compared to other similar Plarail trains. Are they all like this? They are both using the same motor design right? I have not had any apart and only have had a handful pass through my hands but they have all been loud exactly like the one in Ucwepn"s video below at the 3:19 mark. Wonder why, has anyone had one apart? The next time I have a used one I am going to see whats inside but by the looks of what I have seen they look like Shinkansen chassis from the outside.