One Twitter user posted a GIF of a pylon skipping rope with the power line between two other towers. Upon the pylon landing on the ground after each jump, the GIF shakes. For some reason, certain viewers can actually hear the sound of the pylon hitting the ground... Even though there's no sound playing. Weird right?Now Twitter is no stranger to audiovisual illusions – just a couple of years ago we were plagued by the blue\/black vs. white\/gold dress debate. This particular instance is a bit different as there is no one correct answer. Many users on Twitter have been more than willing to add in their own explanation. Some attribute it to the syncopation between the jumping and our own heart beating, some to our brain predicting the expected sound of the landing and therefore triggering the sound in your brain.One expert in the field, Chris Fassnidge, has offered his explanation of the sound – a phenomenon called Visually-Evoked Auditory Response: This is the ability of some people to hear moving objects even though they don’t make a sound, which may be a subtle form of synaesthesia – the triggering of one sense by another.One thing is for sure: we have no idea how it works, and now we can’t stop hearing the noise as we look at it.