Like a musical instrument, the sound of your voice is determined by the shape and size of its parts. The length of your vocal cords, the shape of your nose and the contours of your throat all contribute. The exact timing of the contractions of muscles in your mouth, tongue, larynx and diaphragm are different for everyone – even when they are saying the same words. These things are affected by the accents or cultures that surrounded us when we learned to speak.