1 00:00:00,000 --> 00:00:06,800 All right, I'm here at the Children's Museum of Virginia, located in Portsmouth, Virginia, 2 00:00:06,800 --> 00:00:09,040 and this is Leslie Bowie, the museum's curator. 3 00:00:09,040 --> 00:00:10,040 Hi, Leslie. 4 00:00:10,040 --> 00:00:11,040 Hi, Van. 5 00:00:11,040 --> 00:00:12,800 I understand you want to learn about sounds. 6 00:00:12,800 --> 00:00:17,000 Yeah, I want to learn about how sound works and especially how sound travels. 7 00:00:17,000 --> 00:00:22,000 Well, let's have a look at some of our exhibits and get the answers to those questions. 8 00:00:22,000 --> 00:00:23,000 Okay. 9 00:00:23,000 --> 00:00:28,440 The Children's Museum of Virginia is a place where kids can experience science firsthand. 10 00:00:28,440 --> 00:00:32,040 Here they can feel it, touch it, explore it, learn it. 11 00:00:32,040 --> 00:00:34,920 Let's first consider how sound is produced. 12 00:00:34,920 --> 00:00:39,440 When sounds travel, we actually are hearing how the vibrations affect the air molecules. 13 00:00:39,440 --> 00:00:42,280 A way I can demonstrate this is with a slinky. 14 00:00:42,280 --> 00:00:49,360 Van, hold the other end, please. 15 00:00:49,360 --> 00:00:53,960 What we perceive as sound is due to the alternate squeezing and stretching of molecules through 16 00:00:53,960 --> 00:00:54,960 the air. 17 00:00:54,960 --> 00:00:57,920 This, we refer to as sound waves. 18 00:00:57,920 --> 00:01:02,320 Sound waves travel through the air at 344 meters per second. 19 00:01:02,320 --> 00:01:04,320 They travel slower than light. 20 00:01:04,320 --> 00:01:07,960 You can see this for yourself the next time you see a thunderstorm. 21 00:01:07,960 --> 00:01:11,800 You can work out how far away the storm is from you by timing the interval between the 22 00:01:11,800 --> 00:01:14,080 lightning and the clap of thunder. 23 00:01:14,080 --> 00:01:19,600 A storm is about one mile away for every five seconds you count or one kilometer for every 24 00:01:19,600 --> 00:01:21,760 three seconds. 25 00:01:21,760 --> 00:01:25,760 Now that you know what sound is and how fast it travels, let's do some testing. 26 00:01:26,760 --> 00:01:28,760 What do you notice? 27 00:01:28,760 --> 00:01:31,760 The longer the tube, the lower the pitch. 28 00:01:31,760 --> 00:01:32,760 Well, sure. 29 00:01:32,760 --> 00:01:37,760 The air molecules in the long tube vibrate more slowly, producing a lower sound. 30 00:01:37,760 --> 00:01:40,760 Higher sounds vibrate more quickly. 31 00:01:40,760 --> 00:01:44,760 The difference in the number of vibrations per second we refer to as pitch. 32 00:01:44,760 --> 00:01:45,760 Want to try? 33 00:01:45,760 --> 00:01:46,760 Okay. 34 00:01:55,760 --> 00:01:56,760 Cool. 35 00:01:56,760 --> 00:01:59,760 We can also use a recorder to demonstrate pitch. 36 00:01:59,760 --> 00:02:04,760 You use your fingers to lengthen and shorten the tube and create higher and lower notes. 37 00:02:09,760 --> 00:02:12,760 Well, that's great, but how do you make it louder? 38 00:02:12,760 --> 00:02:16,760 Well, with a recorder, just simply by blowing more air into the tube. 39 00:02:16,760 --> 00:02:20,760 But there's another way to make sounds louder, and that's to focus sound. 40 00:02:20,760 --> 00:02:21,760 Let's come have a look. 41 00:02:21,760 --> 00:02:22,760 Okay. 42 00:02:23,760 --> 00:02:30,760 Here, the parabolic dish collects sound from a huge area and funnels it right to this point. 43 00:02:30,760 --> 00:02:34,760 If you're standing in just the right place, you can even hear a whisper. 44 00:02:36,760 --> 00:02:40,760 So, Van, why was Mr. Murphy only bothered by your sound? 45 00:02:40,760 --> 00:02:41,760 Wait. 46 00:02:41,760 --> 00:02:43,760 Somebody just asked me about Mr. Murphy. 47 00:02:43,760 --> 00:02:45,760 Who asked that question? 48 00:02:45,760 --> 00:02:48,760 Well, Van, I'd like to introduce you to Dr. Lynette Roth. 49 00:02:48,760 --> 00:02:50,760 Dr. Roth is an audiologist. 50 00:02:50,760 --> 00:02:51,760 She specializes in hearing problems. 51 00:02:51,760 --> 00:02:53,760 Oh, you mean like Mr. Murphy? 52 00:02:53,760 --> 00:02:59,760 Well, the question I have is, how come he singled out my band when there were so many other noises in the neighborhood? 53 00:02:59,760 --> 00:03:00,760 It might be, Van. 54 00:03:00,760 --> 00:03:05,760 Like many older people, you couldn't hear the higher frequency of noise that came from the other sound sources. 55 00:03:05,760 --> 00:03:07,760 The higher pitches? 56 00:03:07,760 --> 00:03:08,760 Why? 57 00:03:08,760 --> 00:03:10,760 Let me explain how the ear works first. 58 00:03:11,760 --> 00:03:16,760 Sound waves travel through the air and enter the ear canal, causing the eardrum to vibrate. 59 00:03:16,760 --> 00:03:20,760 The vibrations from the eardrum cause the three bones in the middle ear to move. 60 00:03:20,760 --> 00:03:22,760 The last bone is called the stirrup. 61 00:03:22,760 --> 00:03:24,760 The stirrup is attached to a thin membrane. 62 00:03:24,760 --> 00:03:30,760 On the other side of this membrane is fluid housed inside a curled snail-shaped tube called the cochlea. 63 00:03:30,760 --> 00:03:36,760 The vibrations from the stirrup causes this membrane to flex, which in turn sets the fluid into motion. 64 00:03:36,760 --> 00:03:41,760 The moving fluid tickles thousands of delicate microscopic hair-like cells called cilia. 65 00:03:41,760 --> 00:03:46,760 The cilia convert the vibrations into electric nerve impulses, which the brain interprets as sound. 66 00:03:47,760 --> 00:03:50,760 High frequencies are heard by the cilia at the beginning of the cochlea. 67 00:03:50,760 --> 00:03:53,760 Lower frequencies are heard at the end. 68 00:03:53,760 --> 00:03:57,760 If the sound intensity is too great, or if it happens for a prolonged period of time, 69 00:03:57,760 --> 00:04:00,760 the cells will die at the beginning of the cochlea. 70 00:04:00,760 --> 00:04:03,760 Sound energy, or intensity, is measured in decibels. 71 00:04:03,760 --> 00:04:08,760 Generally speaking, the human ear can comfortably hear between 10 to 80 decibels. 72 00:04:08,760 --> 00:04:12,760 A quiet library typically registers between 40 to 60 decibels, 73 00:04:12,760 --> 00:04:16,760 while a loud rock concert registers above 110 decibels. 74 00:04:16,760 --> 00:04:20,760 Van, it's likely Mr. Murphy has lost some of his ability to hear at high frequencies. 75 00:04:20,760 --> 00:04:25,760 So this explains why Mr. Murphy singled out our band. 76 00:04:25,760 --> 00:04:30,760 Yes, Van, but I'm more concerned about the ear safety of young people, and in particular the noodles. 77 00:04:30,760 --> 00:04:35,760 Be careful how loud you practice your music, not for Mr. Murphy's comfort, but for your safety as well. 78 00:04:35,760 --> 00:04:40,760 You bet. Dr. Roth, Mrs. Bowie, thanks for letting me come over to the Children's Museum of Virginia 79 00:04:40,760 --> 00:04:43,760 to learn about sound and how the ear works. 80 00:04:43,760 --> 00:04:48,760 Okay, I now have a better understanding of the science of sound and how people hear, 81 00:04:48,760 --> 00:04:52,760 but how do I control the amount of sound coming from my garage? 82 00:04:52,760 --> 00:04:55,760 Well, to find the answer to that, we're going to go back to Shelly at NASA Langley 83 00:04:55,760 --> 00:04:57,760 to see what she's learning about noise abatement. 84 00:04:57,760 --> 00:04:59,760 Perhaps she can pick up a tip or two I can use. 85 00:04:59,760 --> 00:05:03,760 Meanwhile, I'll share this information with my band, and I'll catch you later.