0:00:07.314,0:00:08.882 In the mid-16th century, 0:00:08.882,0:00:11.674 Italians were captivated by a type [br]of male singer 0:00:11.674,0:00:14.136 whose incredible range contained notes 0:00:14.136,0:00:17.192 previously thought impossible [br]for adult men. 0:00:17.192,0:00:19.961 However, this gift came at a high price. 0:00:19.961,0:00:22.045 To prevent their voices from breaking, 0:00:22.045,0:00:25.097 these singers had been [br]castrated before puberty, 0:00:25.097,0:00:28.830 halting the hormonal processes [br]that would deepen their voices. 0:00:28.830,0:00:33.791 Known as Castrati, their light, angelic [br]voices were renowned throughout Europe, 0:00:33.791,0:00:39.283 until the cruel procedure that created [br]them was outlawed in the 1800s. 0:00:39.283,0:00:43.483 Though stunting vocal growth can produce [br]an extraordinary musical range, 0:00:43.483,0:00:48.347 naturally developing voices [br]are already capable of incredible variety. 0:00:48.347,0:00:54.734 And as we age our bodies undergo two[br]major changes which explore that range. 0:00:54.734,0:01:00.009 So how exactly does our voice box work,[br]and what causes these shifts in speech? 0:01:00.009,0:01:05.586 The specific sound of a speaking voice is[br]the result of many anatomical variables, 0:01:05.586,0:01:09.631 but it’s mostly determined by the age [br]and health of our vocal cords, 0:01:09.631,0:01:12.227 and the size of our larynxes. 0:01:12.227,0:01:16.237 The larynx is a complex system [br]of muscle and cartilage 0:01:16.237,0:01:18.865 that supports and moves the vocal cords, 0:01:18.865,0:01:22.814 or as they’re more accurately known, [br]the vocal folds. 0:01:22.814,0:01:25.857 Strung between the thyroid [br]and arytenoid cartilages, 0:01:25.857,0:01:31.636 these two muscles form an elastic curtain[br]that opens and shuts across the trachea 0:01:31.636,0:01:34.575 the tube that carries [br]air through the throat. 0:01:34.575,0:01:36.804 The folds are apart when we’re breathing, 0:01:36.804,0:01:39.136 but when we speak, they slam shut. 0:01:39.136,0:01:42.497 Our lungs push air [br]against the closed folds, 0:01:42.497,0:01:46.481 blowing them open and vibrating[br]the tissue to produce sound. 0:01:46.481,0:01:50.279 Unlike the deliberate focus required [br]for playing an external instrument, 0:01:50.279,0:01:53.561 we effortlessly change notes as we speak. 0:01:53.561,0:01:55.440 By pushing air faster or slower, 0:01:55.440,0:01:58.919 we change the frequency and amplitude [br]of these vibrations, 0:01:58.919,0:02:03.070 which respectively translate to the pitch [br]and volume of our voices. 0:02:03.070,0:02:07.605 Rapid and small vibrations create [br]high-pitched quiet tones, 0:02:07.605,0:02:12.743 while slow, large vibrations [br]produce deep, bellowing rumbles. 0:02:12.743,0:02:16.339 Finally, by moving the laryngeal muscles [br]between the cartilages, 0:02:16.339,0:02:19.104 we can stretch and contract those folds 0:02:19.104,0:02:22.644 to intuitively play [br]our internal instruments. 0:02:22.644,0:02:26.483 This process is the same from [br]your first words to your last, 0:02:26.483,0:02:29.466 but as you age, your larynx ages too. 0:02:29.466,0:02:32.776 During puberty, [br]the first major shift starts, 0:02:32.776,0:02:34.987 as your voice begins to deepen. 0:02:34.987,0:02:38.656 This happens when [br]your larynx grows in size, 0:02:38.656,0:02:43.556 elongating the vocal folds and[br]opening up more room for them to vibrate. 0:02:43.556,0:02:47.437 These longer folds have slower, [br]larger vibrations, 0:02:47.437,0:02:50.649 which result in a lower baseline pitch. 0:02:50.649,0:02:53.307 This growth is especially dramatic[br]in many males, 0:02:53.307,0:02:57.053 whose high testosterone levels[br]lead first to voice cracks, 0:02:57.053,0:03:00.167 and then to deeper, more booming voices, 0:03:00.167,0:03:04.258 and laryngeal protrusions [br]called Adam’s apples. 0:03:04.258,0:03:06.793 Another vocal development during puberty 0:03:06.793,0:03:09.714 occurs when the homogenous tissue[br]covering the folds 0:03:09.714,0:03:13.625 specializes into three distinct [br]functional layers: 0:03:13.625,0:03:15.121 a central muscle, 0:03:15.121,0:03:19.713 a layer of stiff collagen wrapped [br]in stretchy elastin fibers, 0:03:19.713,0:03:23.143 and an outer layer of mucus membrane. 0:03:23.143,0:03:25.924 These layers add nuance [br]and depth to the voice, 0:03:25.924,0:03:30.763 giving it a distinct timbre that sets it [br]apart from its pre-pubescent tones. 0:03:30.763,0:03:35.587 After puberty, most people’s voices remain[br]more or less the same 0:03:35.587,0:03:37.713 for about 50 years. 0:03:37.713,0:03:39.633 But we all use our voices differently, 0:03:39.633,0:03:44.440 and eventually we experience the[br]symptoms associated with aging larynxes, 0:03:44.440,0:03:46.118 known as presbyphonia. 0:03:46.118,0:03:48.997 First, the collagen in our folds stiffens 0:03:48.997,0:03:52.717 and the surrounding elastin fibers [br]atrophy and decay. 0:03:52.717,0:03:57.809 This decreased flexibility increases [br]the pitch of older voices. 0:03:57.809,0:04:01.220 But for people who have experienced [br]the hormonal effects of menopause, 0:04:01.220,0:04:06.264 the higher pitch is countered[br]and outweighed by swollen vocal folds. 0:04:06.264,0:04:13.324 The folds increased mass slows their[br]vibrations, resulting in deeper voices. 0:04:13.324,0:04:15.397 All these symptoms are further complicated 0:04:15.397,0:04:18.735 by having fewer healthy [br]laryngeal nerve endings, 0:04:18.735,0:04:23.996 which reduces precise muscle control [br]and causes breathy or rough voices. 0:04:23.996,0:04:28.186 Ultimately, these anatomical changes [br]are just a few of the factors 0:04:28.186,0:04:30.072 that can affect your voice. 0:04:30.072,0:04:31.791 But when kept in good condition, 0:04:31.791,0:04:34.596 your voice box [br]is a finely tuned instrument; 0:04:34.596,0:04:36.669 capable of operatic arias, 0:04:36.669,0:04:38.091 moody monologues, 0:04:38.091,0:04:39.626 and stirring speeches.