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That's 28 00:01:31,040 --> 00:01:36,520 Speaker 1: the Great Courses Plus dot com slash brain Stuff. Welcome 29 00:01:36,520 --> 00:01:43,640 Speaker 1: to brain Stuff from How Stuff Works. Hello brain Stuff. 30 00:01:43,640 --> 00:01:46,800 Speaker 1: I'm Christian Saga, and today we're going to talk about 31 00:01:46,840 --> 00:01:49,400 Speaker 1: the human voice. You might have noticed that if you're 32 00:01:49,440 --> 00:01:52,240 Speaker 1: talking to a group of five year old boys and girls, 33 00:01:52,600 --> 00:01:55,880 Speaker 1: let's say you're asking them for advice about your investment portfolio, 34 00:01:56,280 --> 00:01:58,960 Speaker 1: there's not a big difference between the pitch of the 35 00:01:59,000 --> 00:02:02,520 Speaker 1: girl's voices and the pitch of the boy's voices. Yet, 36 00:02:02,800 --> 00:02:05,240 Speaker 1: if you talk to a group of thirty five year 37 00:02:05,240 --> 00:02:08,440 Speaker 1: old men and women, you notice that the men's voices 38 00:02:08,480 --> 00:02:12,080 Speaker 1: are on average a good bit deeper than the women's voices. 39 00:02:12,639 --> 00:02:15,560 Speaker 1: So why is that and how does it happen? Well, 40 00:02:15,600 --> 00:02:18,880 Speaker 1: first off, let's acknowledge that everyone is a special and 41 00:02:19,040 --> 00:02:22,120 Speaker 1: unique butterfly. And there's no rule about how men and 42 00:02:22,200 --> 00:02:27,359 Speaker 1: women's voices should sound, But on average, adult men's voices 43 00:02:27,480 --> 00:02:32,040 Speaker 1: have what's known as a lower fundamental frequency than adult 44 00:02:32,160 --> 00:02:36,880 Speaker 1: women's voices. The fundamental frequency is simply the scientific term 45 00:02:37,000 --> 00:02:41,359 Speaker 1: for how high or low a person's natural speaking voice sounds. 46 00:02:41,760 --> 00:02:45,040 Speaker 1: Sound frequency is measured in hurts, which is a measure 47 00:02:45,040 --> 00:02:48,359 Speaker 1: of how many times something happens in a second. So 48 00:02:48,680 --> 00:02:51,560 Speaker 1: a sound wave that vibrates a hundred times per second 49 00:02:51,600 --> 00:02:54,880 Speaker 1: produces a tone of a hundred hurts. The more cycles 50 00:02:54,880 --> 00:02:58,040 Speaker 1: per second, the higher the pitch. According to the National 51 00:02:58,080 --> 00:03:01,400 Speaker 1: Center for Voice and Speech, bay bees usually cry at 52 00:03:01,400 --> 00:03:05,960 Speaker 1: a frequency of around five hundred hurts. Children have speaking 53 00:03:06,000 --> 00:03:08,400 Speaker 1: frequencies in the range of two hundred and fifty to 54 00:03:08,480 --> 00:03:12,000 Speaker 1: four hundred hurts. By the time of adulthood. However, men 55 00:03:12,440 --> 00:03:16,320 Speaker 1: have an average fundamental frequency of about one hundred and 56 00:03:16,320 --> 00:03:20,240 Speaker 1: twenty five hurts and women about two hundred hurts. What 57 00:03:20,360 --> 00:03:24,320 Speaker 1: happened here? What why the big difference? Okay, to understand 58 00:03:24,320 --> 00:03:27,120 Speaker 1: why men's voices end up lower than women's voices, we 59 00:03:27,160 --> 00:03:29,680 Speaker 1: need to look at how the body produces sounds. So 60 00:03:30,040 --> 00:03:33,120 Speaker 1: let's take a magical journey to the inside of your neck. 61 00:03:33,960 --> 00:03:36,560 Speaker 1: Leading from your lungs to the cavity behind your mouth 62 00:03:36,640 --> 00:03:39,480 Speaker 1: and nose is a pipeline called the tray chia. You 63 00:03:39,560 --> 00:03:41,600 Speaker 1: use it to breathe. At the top of the tray 64 00:03:41,640 --> 00:03:44,400 Speaker 1: chia is a hollow organ called the larynx, or in 65 00:03:44,520 --> 00:03:49,200 Speaker 1: common parlance, the voice box. The larynx is amazing. For example, 66 00:03:49,200 --> 00:03:51,400 Speaker 1: when you swallow food. It is a part of the 67 00:03:51,480 --> 00:03:54,880 Speaker 1: larynx called the epiglottis that closes off your tra chea 68 00:03:55,120 --> 00:03:58,000 Speaker 1: and keeps you from getting gummy bears in your lungs. 69 00:03:58,400 --> 00:04:01,040 Speaker 1: The larynx is also what allows us to make sound 70 00:04:01,120 --> 00:04:03,720 Speaker 1: for talking or singing. To do this, you use your 71 00:04:03,800 --> 00:04:06,280 Speaker 1: lungs to push a column of air through the larynx 72 00:04:06,280 --> 00:04:09,960 Speaker 1: while using your laryngeal muscles to press together a pair 73 00:04:09,960 --> 00:04:14,160 Speaker 1: of membranes called the vocal folds, or more commonly, your 74 00:04:14,240 --> 00:04:17,920 Speaker 1: vocal chords. When you close the vocal folds like this, 75 00:04:18,160 --> 00:04:21,680 Speaker 1: the air you push out through them makes them vibrate, 76 00:04:21,839 --> 00:04:25,880 Speaker 1: and this vibration leads to sound. So the next time 77 00:04:25,960 --> 00:04:29,240 Speaker 1: you're just shrieking and shrieking until the cashier finally accepts 78 00:04:29,240 --> 00:04:33,800 Speaker 1: your expired coupon, thank your larynx. There are several factors 79 00:04:33,839 --> 00:04:36,880 Speaker 1: that can all have some effect on the fundamental frequency 80 00:04:36,920 --> 00:04:39,760 Speaker 1: of a person's voice, like the size of the larynx 81 00:04:39,800 --> 00:04:43,359 Speaker 1: and the differential development of facial bones and muscles. But 82 00:04:43,920 --> 00:04:47,159 Speaker 1: the most important factor to talk about is the length 83 00:04:47,320 --> 00:04:50,560 Speaker 1: of the vocal folds. If you pluck a string, the 84 00:04:50,720 --> 00:04:53,479 Speaker 1: length of the string affects the frequency of the note 85 00:04:53,520 --> 00:04:56,479 Speaker 1: that plays. Think about a guitar. When you press a 86 00:04:56,560 --> 00:04:59,440 Speaker 1: string down to a higher fret. On a guitar, you 87 00:04:59,480 --> 00:05:01,600 Speaker 1: shorten the length of the part of the string that 88 00:05:01,720 --> 00:05:05,159 Speaker 1: vibrates when you pluck it, and this produces a higher note. 89 00:05:05,520 --> 00:05:08,400 Speaker 1: The same thing happens inside your larynx. The longer the 90 00:05:08,480 --> 00:05:12,440 Speaker 1: vocal fold, the lower the note. During puberty, both boys 91 00:05:12,440 --> 00:05:15,719 Speaker 1: and girls experience growth of the vocal folds, leading to 92 00:05:15,800 --> 00:05:20,680 Speaker 1: lower voices, but the male hormone testosserone, which is released 93 00:05:20,760 --> 00:05:25,200 Speaker 1: by the testicles during puberty, typically causes boys vocal folds 94 00:05:25,400 --> 00:05:29,440 Speaker 1: to grow longer and thicker than girls. On average, adult 95 00:05:29,480 --> 00:05:32,920 Speaker 1: women have vocal folds somewhere around ten millimeters long, while 96 00:05:32,960 --> 00:05:38,040 Speaker 1: adult men have vocal folds in the neighborhood of sixteen millimeters. Consequently, 97 00:05:38,360 --> 00:05:41,960 Speaker 1: women are up there on the upper frets soloing into 98 00:05:42,000 --> 00:05:44,440 Speaker 1: oblivion like a high school kid who just learned how 99 00:05:44,480 --> 00:05:48,119 Speaker 1: to play eruption by Van Halen, and men are letting 100 00:05:48,160 --> 00:05:51,720 Speaker 1: the open strings ring like the intro of Nothing Else 101 00:05:51,800 --> 00:05:55,200 Speaker 1: Matters by Metallica. Now here's some bonus information for you. 102 00:05:55,480 --> 00:05:58,640 Speaker 1: Everyone knows what happens when you inhale some helium from 103 00:05:58,640 --> 00:06:01,240 Speaker 1: a party balloon or you know, straight from an industrial 104 00:06:01,279 --> 00:06:05,640 Speaker 1: helium transport truck. Your voice pitch gets higher. This is 105 00:06:05,680 --> 00:06:08,880 Speaker 1: because helium is less dense than air. But did you 106 00:06:08,960 --> 00:06:12,239 Speaker 1: know you can reverse the effect and give yourself a deep, 107 00:06:12,400 --> 00:06:15,960 Speaker 1: booming bridge troll voice by breathing a gas with a 108 00:06:16,080 --> 00:06:21,440 Speaker 1: higher density than your air, like zenon or sulfur hexafluoride. 109 00:06:21,800 --> 00:06:24,680 Speaker 1: But remember, your body needs air to live, and breathing 110 00:06:24,720 --> 00:06:27,720 Speaker 1: anything other than air can be dangerous, so don't try 111 00:06:27,720 --> 00:06:35,240 Speaker 1: this at home. Check out the brain stuff channel on YouTube, 112 00:06:35,320 --> 00:06:37,479 Speaker 1: and for more on this and thousands of other topics, 113 00:06:37,640 --> 00:06:52,960 Speaker 1: visit how stuff works dot com.