The same principles that apply to vibrating strings apply to any vibrating object. The vocal folds are made to vibrate by air passing over them under pressure from the lungs. The thickness, width and tension of the folds, all affect the sound that we make when we speak or sing. The lower the sound we make, the wider, or thicker, or looser the vocal folds (or any combination of the three). People with thicker or wider vocal folds have deeper natural voices.
Unlike the string experiment in the laboratory, however, human beings donΓÇÖt have any direct control over the properties of their vocal folds. We canΓÇÖt consciously stretch them to make them wider, or increase their tension. Indeed, good singing requires a relaxed throat, leaving the folds to vibrate freely according to the pressure of air passing over them.
