Towards the bottom of this article about synaesthesia - a condition where senses intermingle -- is a short animation to "test" people who may have the condition. Turns out we have it mildly -- not to the point where we hear colors, but we have always "heard" patterns and math, and found it odd when we realized the other day this is not a normal phenomenon. Now we feel really odd. The video sounds like a very very very loud murmured heartbeat to us. If you can hear it, what does it sound like to you?