Some time ago I read that, when sound waves reach the ear drum, they cause a series of bones -- one placed after another -- to vibrate, and these vibrations ultimately reach the nerves that lead to the brain. Correct me if I'm wrong, but I assume that only one vibration can move through these bones at any one time. If that is so, then when two or more sound waves reach the ear drum -- and thus the bones -- at the same time, they combine together into one vibration that proceeds to move through the bones to the nerves. Yet somehow we're able to hear two or more sounds simultaneously. Does anyone know how this works?