I've recently become aware that whenever there's a constant sound/noise, such as a hairdryer, running water, a shredder, vacuum cleaner etc., my 15 month old DS will shake his head from side to side while watching the source of the noise.
Has anyone ever experienced this before? He's always been sensitive to loud noises since he was newborn, used to cry when people sneezed or blew their noses, maybe he just has sensitive ears?