Book 14 activities
Try it at home: 150 science activities from Book 14
Every question in A Million Whys Book 14, The Sound Expedition, ends with a "Think like a scientist" idea. Here they are in one place. Each one links to its question page, with the video and the full answer.
Expedition 1: Vibrations & Waves (25)
1. Why Does Every Sound Begin with Something Shaking?
Stretch a rubber band around an open box or a plastic container and pluck it gently. Watch the band blur as it vibrates. Now touch it lightly with a finger to stop it. What happens to the sound?
2. Why Does Your Throat Tickle When You Hum?
Put your fingertips lightly on your throat and hum a low note, then a high note. Feel how the buzz changes. Now whisper and see if the buzzing stops.
3. Why Does a Ruler Buzz When You Flick It Off the Edge of a Desk?
Hold a ruler flat on a desk with half of it hanging over the edge. Gently flick the end and listen. Then flick a little harder. What changes? Keep the ruler away from your face.
4. What Is a Sound Wave Actually Made Of?
Stand ten dominoes in a row, close together, and tip over the first one. Watch the “push” run along the row. Which parts moved, and which part just kept going?
5. Why Does a Slinky Show How a Sound Wave Moves?
Stretch a slinky along a smooth floor or table with a friend holding the other end. Push a few coils together and let go. Watch the squeezed part zoom to the end and bounce back.
6. How Are Water Ripples Like Sound Waves?
Fill a tub or sink with water and let it settle. Drop a small pebble in the middle and watch the ripples. Float a cork on top. Does it travel with the wave or just bob?
7. Why Does Rice Dance on Plastic Wrap When You Bang a Pot Nearby?
Stretch plastic wrap over a bowl and sprinkle a spoonful of rice or sugar on top. Tap a pot gently with a wooden spoon a short distance away. Watch the grains jump. Keep your ears away from the pot.
8. Why Does a Tuning Fork Keep Ringing for a While?
If you can borrow a tuning fork (from a music room or science kit), tap it lightly on your knee and touch the tips to the surface of some water in a small bowl. What do you see?
9. Why Can You Feel Deep Bass Thumping in Your Chest?
Put your hand flat on a table near a speaker playing soft music with a deep beat. Can you feel the table humming? Never press a speaker against your body or ears.
10. Why Does Pushing a Swing at Just the Right Moment Work So Well?
With a grown-up at the playground, give a friend on a swing a gentle push at the end of every swing. Then try pushing at the wrong time. When does it work best?
Do this with a grown-up11. Why Does a Tuning Fork Sound Louder When You Touch It to a Table?
With a grown-up, hold the base of a running electric toothbrush on a wooden table and then in the air. Listen to the buzz each time. Which is louder? Do not put it in your mouth.
Do this with a grown-up12. Why Can a Tin-Can Phone Carry a Voice?
With a grown-up, make a phone from two paper cups and a long string, tied through small holes. Pull the string tight and talk quietly. What happens if you let it go slack or pinch it?
Do this with a grown-up13. What Does It Mean When We Say a Sound Has a Frequency?
Tap a pencil on the table two times every second. That is two hertz. Now try four taps a second. How would you make one hundred taps a second? Why can’t you do it by hand?
14. Why Do Puddles Shiver When a Heavy Truck Rumbles By?
Put a glass of water on a table and watch the surface. Gently thump the floor with your foot nearby, or have a friend walk past. Do you see ripples? Do heavier steps make bigger ripples?
15. Why Do Wood, Metal, and Glass Sound Different When You Tap Them?
Tap a wooden spoon gently on a wooden board, a metal pot lid, a plastic container, and a cardboard box. Sort them from “ring” to “thud.” Ask a grown-up before tapping glass.
Do this with a grown-up16. Why Does a Bottle Hum When You Blow Across the Top?
Blow across the top of different empty bottles, with your lips close to the opening. Which bottle gives the lowest hum? Which gives the highest hum? Line them up from low to high.
17. Why Does a Fan Hum Higher When It Speeds Up?
With a grown-up, listen to a fan on low, medium, and high speeds, and describe the sound each time. Do not touch the blades. Hum along with each speed and compare your notes.
Do this with a grown-up18. Why Does a Card in Bicycle Spokes Make a Buzzing Motor Sound?
With a grown-up, hold a clothespin and card near the wheel of an upside-down bike. Spin the wheel slowly, then faster. Keep fingers away from spokes. What changes about the sound?
Do this with a grown-up19. Why Do Refrigerators Hum?
Turn off the TV and listen quietly in your kitchen for one minute. Write down all the humming and buzzing sounds you hear. Which ones come from vibrating machines?
20. Why Can You Hear a Mosquito's Wings but Not a Slowly Flapping Bird's?
Wave a ruler slowly through the air and listen. Then hold it on a desk’s edge and flick it so it buzzes. Why does one make a tone and the other not?
21. Why Do Sound Waves Push and Squeeze Instead of Going Up and Down?
Draw two pictures: one of squeezed and stretched coils for a sound wave, and one of a rope shaken up and down. Label which direction the wave travels in each.
22. Why Does a Stadium Wave Move Across the Crowd While the People Stay Put?
With friends or family in a row or a circle, do a wave: each person raises their arms in turn. Who moves? Who stays put? What is the wave carrying?
23. Why Do Two Nearly Matching Sounds Make a Wobbling Wah-Wah?
With a friend, each hum the same note as steadily as you can, standing close together. Then slowly change one note slightly. Do you hear a wah-wah wobble? What happens when you match?
Do this with a grown-up24. Why Can't We See Sound Waves?
With a grown-up and a free sound-wave app on a phone, whistle softly, then hum a low note. Watch how the wiggly line changes. Which sound makes the lines closer together?
Do this with a grown-up25. Why Does a Fast-Shaking Object Look Blurry?
Pluck a rubber band stretched over a container. Watch the blur. Then ask a grown-up to film it in slow motion on a phone and watch it again. What can you see in the slow-motion video?
Do this with a grown-upExpedition 2: Loud, Soft, High & Low (25)
26. Why Are Big Things Usually Lower in Sound than Small Things?
Tap a large pot, a small pot, and a tiny cup with a wooden spoon. Put them in order from the lowest sound to the highest. Is it the same order as biggest to smallest?
27. What Makes One Sound Louder than Another?
Stretch a rubber band over a box. Pluck it softly and then a bit harder. Watch how wide the blur gets. Which one is louder? Which one has the bigger wiggle?
28. What Makes a Sound High or Low?
Stretch a rubber band around a box and pluck it. Pull it tighter with your other hand and pluck again. Is the second sound higher or lower? Why?
29. Why Do Mosquitoes Whine High While Bumblebees Buzz Low?
Use a small piece of card and a big piece of card as fans. Flap each one as fast as you can. Which one can you wave faster? Which one would make a higher pitch?
30. Why Does a Ruler Twang Lower When More of It Hangs Over the Edge?
Tie a washer or a small weight to a string. Let it swing as a pendulum with a long string and then a short string. Which swings faster? Now flick a ruler at the long and short lengths.
31. Why Does the Sound of Pouring Water Get Higher as the Glass Fills?
Pour water into a tall plastic bottle at the sink with your eyes closed. Listen as it fills. Can a friend tell when the bottle is almost full just by listening?
32. What Do Decibels Measure?
Make a loudness chart with a long line from 0 to 140. Mark where a whisper, a fridge hum, talking, a vacuum cleaner, and a siren would go. Ask a grown-up to check your guesses.
Do this with a grown-up33. Why Do 10 More Decibels Sound About Twice as Loud?
A quiet room is about 30 dB and a vacuum is about 70 dB. How many 10 dB steps is that? If each step sounds twice as loud, about how many times louder does the vacuum seem?
34. Why Does Cupping Your Hands Behind Your Ears Help You Hear?
Ask a friend to whisper from across the room. Listen with your ears normal, then cup your hands behind them. Try rolling a paper into a cone and hold the narrow end near your ear.
35. Why Does Fresh Snow Make Everything Sound So Quiet?
Drop a marble from a low height onto a bare table. Then drop it onto a thick folded towel. Which makes a quieter sound? Why does the soft surface help?
36. Why Do Carpets and Curtains Make a Room Sound Quieter?
Clap once in a bathroom with hard tiles and once in a bedroom with carpet and curtains. Which room sounds more echoey? Which sounds softer or deader?
37. Why Do Deep Rumbles Carry Farther than Squeaks?
Listen to a faraway noise, like music from a neighbor’s car or house. Which part do you hear best from far away, the deep bass or the high sounds? What gets lost?
38. Why Can't We Hear a Dog Whistle?
Draw a number line from 0 to 60,000 hertz. Mark where people hear, from 20 to 20,000. Mark where a dog hears. Where would you put a dog whistle?
39. Why Would the Quietest Room in the World Feel Strange?
Sit in the quietest room in your home for two minutes with your eyes closed. List every sound you can notice. Did you hear any sounds that you usually miss?
40. Why Is It Hard to Hear a Friend in a Noisy Room?
Have a friend say five secret words in a normal voice. Try once in a quiet room and once while a radio plays quietly. How many words do you get right each time?
41. Why Do People Talk Louder When It Is Noisy?
Read a sentence aloud in a quiet room. Then read it again while a friend hums steadily nearby. Did your voice get louder without trying? Ask your friend what they noticed.
42. How Can Two Sounds Cancel Each Other Out?
On tracing paper, draw a wiggly wave. Flip the paper over and draw the mirror image. Hold the two together and look at the sum. What do you notice about the up and down parts?
43. Why Do Foghorns Make Deep Sounds?
Have a friend walk slowly away down a hallway or across a field. Hum a very low note and then a high one. Which one can they still hear when they are farther away?
44. Why Do Longer Wind-Chime Tubes Ring Lower?
Look at wind chimes outside a house or in a store. Compare tube lengths. Does the longest tube sound the lowest? Gently tap it with a pencil to check.
Do this with a grown-up45. Why Can You Hear the Ocean in a Seashell?
Hold a mug, a paper cup, and a seashell (if you have one) up to your ear in turn. Does each sound a little different? What happens if you cover the open side with your hand?
46. Why Does a Sound Seem Softer When You Are Farther Away?
Have a friend tap a spoon on a pot lid at the same strength while standing 1, 2, 4, and 8 big steps away. Close your eyes and rank how loud each seems.
47. Why Do You Hold Your Breath When You Try to Hear a Tiny Sound?
Put a ticking clock or a watch across a room. Walk until you can hardly hear it. Now hold your breath or stay super still. Can you hear it a bit better?
48. Why Do Phone Calls Make Voices Sound Thinner?
Ask a grown-up to call you on a phone from another room. Compare how their voice sounds on the phone with how it sounds in person. What is missing from the phone version?
Do this with a grown-up49. Why Do Sounds Seem Muffled Through a Wall?
Play quiet music on a phone inside a cardboard box and listen. Then wrap the phone in a thick towel and put it inside the box. Which blocks more sound? Why?
50. How Can You Hear Someone Talking From Around a Corner?
Have a friend talk quietly behind a nearly closed door or around a corner. Can you hear them? Does their voice sound deeper or muddier than usual?
Expedition 3: Sound Makers & Machines (25)
51. Why Does a Megaphone Make Your Voice Carry Farther?
Roll a sheet of paper into a cone and speak through the narrow end toward a friend across a yard. Then ask them to stand behind you. Where is your voice easier to hear?
52. Why Do Small Speakers Sound Thin and Big Speakers Sound Full?
Play the same song at a low volume on a phone and then on a bigger speaker. What parts are easier to hear on the bigger speaker? Which one has more deep thump?
53. Why Does a Microphone Squeal When It Gets Close to a Speaker?
Draw a loop with arrows: voice, microphone, amplifier, speaker, and back to the microphone. Mark three ways to break the loop. Why does turning down the volume help?
54. Why Does a Bell Keep Ringing After You Hit It?
Hold a metal pot lid by its handle or knob and tap it gently with a wooden spoon. Listen to how long it rings. Then touch the lid with your hand to stop it. What changes?
55. Why Do Sirens Rise and Fall in Pitch?
Make your own siren with your voice by sliding from a low hum to a high one and back. Try it slowly, then quickly. Why is a changing sound harder to ignore than a steady one?
56. Why Does a Phone Buzz in Vibrate Mode?
Ask a grown-up to put a phone on vibrate and call it. Place it on a wooden table, then on a soft pillow. Where is the buzz louder? Why does the table make more noise?
Do this with a grown-up57. Why Are Vacuum Cleaners and Hair Dryers So Noisy?
Blow gently through a straw, and then squeeze the end of the straw flat and blow again. Does the sound change when the air has to squeeze through a narrow gap?
58. Why Do Some Quiet Electric Cars Hum on Purpose?
Always stop, look, and listen before crossing a road. Practice with a grown-up. Then draw a design for a car sound that is easy to notice but not annoying. What would it sound like?
Do this with a grown-up59. How Can a Needle in a Groove Play a Song?
Run your thumbnail slowly along the teeth of a comb, then faster. Listen to the clicks join together into a buzzing tone. How is this like a needle in a groove?
60. Why Does Snapping Your Fingers Make a Snap?
Try snapping with dry fingers, and then with a little soap on them. Does the snap sound the same? Where do you think the sound comes from?
61. Why Does a Clap Make a Sharp Crack?
Clap with flat hands and then with cupped hands. Which one makes a sharper crack? Which one sounds lower and hollow? What is trapped between your hands in the second one?
Do this with a grown-up62. Why Does Bubble Wrap Crack When You Squeeze It?
Squeeze small and big bubbles one at a time and listen. Which size makes a higher pop? Keep the wrap away from your ears and put it in the recycling when you are done.
63. Why Does Velcro Make a Ripping Sound?
Peel a piece of Velcro apart slowly and then quickly. How does the sound change? Look at both sides with a magnifying glass. Can you spot the hooks and loops?
64. Why Does a Soda Can Go Psst When You Open It?
With a grown-up, open a chilled can that has not been shaken and listen for the hiss. Pour a bit into a glass and watch the bubbles rise. Why does the hiss stop after a moment?
Do this with a grown-up65. Why Do Ice Cubes Crackle in a Drink?
Drop an ice cube into a glass of room-temperature water and listen closely. Then try a cube that has been sitting out for a few minutes. Which one crackles more? Why?
66. Why Does Rain Sound Louder on a Metal Roof than on Grass?
Let a few drops of water fall from a spoon onto a metal baking tray, then onto the same tray with a towel on top, then onto dirt in a tub. Which sounds the loudest?
67. Why Do Squeaky Doors and Sneakers Squeak?
Slowly drag a damp fingertip across a clean window. Listen for a squeak and change your speed. Ask a grown-up to oil a squeaky hinge. Does the squeak go away?
Do this with a grown-up68. Why Does Wind Howl Around a House?
On a windy day, listen near corners, fences, and gaps under doors. Where does the wind make a sound? Draw a map of the noisy spots and think about their shapes.
69. Why Do Footsteps Sound Different on Different Floors?
Walk across tile, wood, and carpet in socks, then in hard shoes. Close your eyes and listen. Can you tell which floor you are on? Put the floors in order from loudest to quietest.
70. Why Does a Balloon Squeal When You Let the Air Out?
With a grown-up, blow up a balloon only a little and pinch the neck to let the air out slowly. Stretch the neck wider and narrower to change the pitch. Keep it away from your eyes and ears.
Do this with a grown-up71. Why Does a Spoon Hung on a String Sound Like a Big Bell?
Tie a metal spoon to the middle of a long string. Wrap the string ends around your index fingers, and gently touch your fingertips to the outside of your ears. Lean forward and let the spoon bump the table.
Do this with a grown-up72. Why Does a Phone Sound Louder in a Bowl?
Play quiet music on a phone. Put the phone on a table, then in an empty bowl, then in a mug. Which is loudest? Which direction does the sound go in the bowl?
73. Why Does Crunchy Food Sound So Loud When You Chew It?
Eat a crunchy cracker, then a soft piece of bread. Try covering your ears with your hands too. Which food is louder to you? Ask a friend sitting nearby if it sounds as loud to them.
74. Why Do Cars Need Mufflers?
Blow into your palm through an empty paper-towel tube and notice the sound and the air. Now stuff cotton or tissue loosely in the tube and try again. Is it quieter?
75. Why Does a Jar Lid Pop When You Open It?
Look at a new jar with a safety button. Press the dome and listen for the click. Ask a grown-up to open a new jar and listen for the pop. Why does the pop happen only once?
Do this with a grown-upExpedition 4: How Sound Travels (25)
76. Why Can't Sound Travel Through Empty Space?
Write three ways astronauts could talk to each other in space without sound traveling through air: hand signals, lights, and radio. Then play a silent charades game with a friend using only gestures.
77. Why Does Sound Travel Faster in Water than in Air?
In a bath with a grown-up nearby, tap the side of the tub gently with a spoon while your ears are above water, then with your ears under water. Which sounds sharper? Which sounds different?
Do this with a grown-up78. Why Does Sound Travel Fastest Through Solid Metal?
Find a long metal railing or pole outdoors. Have a friend gently tap one end with a coin while you rest your ear lightly on the other end. Do you hear two taps? Which comes first?
Do this with a grown-up79. Why Does a Siren Sound Higher as It Comes Toward You and Lower as It Goes Away?
Stand well back from a road with a grown-up and listen as a car or bike goes by. Can you hear the pitch drop as it passes? Try to hum the high note before and the low note after.
Do this with a grown-up80. Why Can You Hear a Train Through the Rails Before You Hear It in the Air?
Work it out: a train is 1 kilometer away. Sound in steel goes about 5,000 meters a second and in air about 340. How long does each take? Which arrives first, and by how many seconds?
81. Why Does a Whip Crack?
Lay a long soft rope on the floor and flick one end sideways. Watch the wave run along to the far end. Does it look like it speeds up? Feel how your flick travels to the end.
82. Why Does a Jet Flying Faster than Sound Make a Boom?
Drag your finger through a tub of still water slowly and then fast. Watch the V-shaped wake that forms when you move fast. How does it look like a jet’s shock wave?
83. Why Does Sound Carry Farther on a Cold, Still Morning?
Notice faraway sounds, like trains or highways, on a calm cold morning and on a windy afternoon. Write down which sounds you can hear on each day. When is it easier to hear faraway things?
84. Why Do Voices Carry So Far Across a Calm Lake?
With a grown-up at the edge of a calm pond or lake, talk to a friend at a distance in a normal voice. How far can they still hear you? Compare that with talking along a wooded path.
Do this with a grown-up85. Why Do Voices Sound So Strange Underwater?
In a bath with a grown-up nearby, put your ears under the water while a friend talks above. How does their voice sound? Hum underwater yourself. How does that compare?
Do this with a grown-up86. Why Is It Hard to Tell Where a Sound Is Coming From Underwater?
Close your eyes and have a friend tap a spoon on a pot lid in different places around you. Point to each sound. Then cover one ear and try again. How does your accuracy change?
87. Why Does Bass Travel Through Walls When High Sounds Don't?
Play quiet music in one room with the door closed and listen from the next room. Which parts of the music can you hear? Which parts disappear? Write down what you notice.
88. Why Is Sound a Little Faster on a Hot Day?
Use the clue that sound gains about 0.6 meters per second for each degree. How fast is sound at -20 degrees on a cold Canadian morning? How fast on a 35-degree summer day?
89. How Fast Does Sound Travel?
During a storm, stay safely indoors. When you see a flash through the window, count the seconds until the thunder rumbles. Every three seconds is about one kilometer away. How far was it?
90. Why Can a Long Tube Carry a Whisper?
Whisper into one end of a long garden hose or cardboard tube while a friend holds the other end to their ear from across the yard. Can they hear you? Compare it without the hose.
91. Why Can Astronauts Talk to Each Other on a Spacewalk?
Draw the chain of steps from voice to ear for two astronauts: voice, microphone, radio waves, speaker, ear. Which steps use sound? Which steps use radio waves?
92. Why Do Scuba Divers Use Hand Signals Instead of Talking?
With a friend, practice three signals without speaking: “okay,” “up,” and “stop.” Can you carry on a short chat using only gestures?
93. Why Do Highways Have Tall Walls Beside Them?
Play a quiet tone on a phone. Stand a big book upright between you and the phone. Sit low behind it and listen, then stand up so your ears are above the top. How does the sound change?
94. Why Can a Whisper Travel Along a Curved Wall?
Hold a ticking watch near the inside edge of a large metal bowl. Put your ear to the inside edge on the other side. Can you hear the tick traveling around the curve?
95. Why Does a Plane Seem to Be in a Different Place than Its Sound?
When a plane flies overhead on a clear day, point to where the sound seems to come from. Then find the plane itself with your eyes. Are the two spots the same? Which one is ahead?
96. Why Does a Crowd of People Sound Like a Steady Roar?
With four or five friends, everyone say a different word at the same time. Can you make out any single word? Then everyone say the same word at the same time. What changes?
97. Why Do Voices Sound Thin High Up on a Mountain?
Compare talking in a small closed room with talking in a big open field. Where does your voice seem fuller and louder? What is bouncing back in the room that is missing outdoors?
Do this with a grown-up98. Why Does Snow Squeak When It Is Very Cold?
On a very cold day, walk on fresh snow and listen. On a warmer day, listen again. Write down the temperatures and which day was squeakier.
99. Why Does a Frozen Lake Sometimes Make Strange Pew-Pew Sounds?
Stretch a slinky and tap one end with a metal spoon. Listen for the falling zap. This is the same kind of effect, with high sounds racing ahead of low ones.
100. Why Do Some Beaches Have Singing Sand?
At the next beach you visit, shuffle your feet through dry sand and wet sand. Do you hear a difference? Compare with different beaches, and note the color and grain size.
Expedition 5: Echoes & Sonar Clues (25)
101. Why Can You Hear a Clear Echo in a Canyon but Not in a Forest?
Find a big flat wall across an empty field or schoolyard, at least 20 big steps away. Say a short word in a loud, clear voice (not a scream) and listen. Try the same near some trees.
102. Why Does Your Voice Sound Bigger in a Bathroom?
In your bathroom, hum a note and slowly slide it from low to high. Listen for a note that suddenly seems extra loud and boomy. That is a pitch the room likes to vibrate at.
103. Why Does a Shout in a Tunnel Keep Ringing?
With a grown-up, clap once in a stairwell, a gym, or an underpass and count how many seconds the sound lingers. Compare that with clapping in a carpeted room. Which one lasts longer?
Do this with a grown-up104. How Can You Use an Echo to Measure Distance?
Work this out: you clap, and the echo comes back after 2 seconds. How far away is the cliff? Show the steps. Then check what happens if the echo comes back after only half a second.
105. Why Do Car Parking Sensors Beep Faster as the Car Gets Closer?
Play the parking-sensor game: close your eyes while a friend slowly walks toward you holding a clipboard. Beep faster as they get closer. Then switch roles. How could your voice tell the distance?
106. How Can Some People Use Clicking Sounds to Sense Walls and Doorways?
Sit in a quiet room with your eyes closed. Make soft tongue clicks while a friend holds a big board close, then far, in front of you. Can you tell when it is near? Stay seated, so you are safe.
107. What Is Ultrasound, and How Do Bats and Doctors Use It?
Ask a grown-up if they have an ultrasound picture, for you or a relative. Look at it together. Then explain how a wand sends sound pulses into the body and listens for the echoes that make the picture.
Do this with a grown-up108. Why Can a Shout Take Seconds to Bounce Back From a Far-Away Mountain?
Work it out: you shout toward a mountain and hear the echo after 6 seconds. Sound goes 343 meters each second. How far away is the mountain? Show your steps. Divide by two at the end.
109. Why Do Recording Studios Have Foam Wedges on the Walls?
Ask a grown-up to record a short message on a phone in a bathroom and then again in a closet full of clothes. Listen to both. Which one sounds clearer and why?
Do this with a grown-up110. Why Can't You Hear an Echo in a Small Room?
Use a tape measure to find how far you are from the wall across your bedroom. Use the clue that sound goes 343 meters a second. How long would an echo take? Is it enough to hear?
111. Why Does Clapping Between Two Flat Walls Make a Zinging Sound?
Clap in an empty room with two flat walls. Then hang a thick blanket over one wall and clap again. Does the zing change? Why does the soft blanket stop the bouncing?
112. Why Can Tapping a Wall Tell You Where the Hidden Beams Are?
With a grown-up, tap along a wall using your knuckle, every few centimeters. Listen for places that sound hollow and places that sound solid. Mark each place with a small piece of tape.
Do this with a grown-up113. Why Do People Tap Things to Check If They Are Cracked or Hollow?
At the grocery store, ask a grown-up to let you tap a few melons or squashes. Which ones sound hollow and deep? Which sound dull? Can you guess which are ripe?
Do this with a grown-up114. How Do Plumbers Find a Leak in a Pipe Using Sound?
With a grown-up, run some water in a sink and hold a cup against the wall near the pipe. Press your ear to the cup’s bottom. Is the sound louder than without the cup? Move around to find the loudest spot.
Do this with a grown-up115. How Can Scientists Use Sound to Measure How Thick Ice Is?
Work it out: a pulse goes down and returns after 0.0004 seconds. Sound in ice goes about 3,500 meters each second. How thick is the ice? Remember to divide by two.
116. Why Can You Tell How Big a Room Is with Your Eyes Closed?
Sit with your eyes closed in different rooms of your home with a grown-up. Clap once in each and listen. Guess how big and how soft the room is. Open your eyes to check.
Do this with a grown-up117. Why Do You Sometimes Hear Your Own Voice Echo on a Phone Call?
With a grown-up and a friend or relative, call on speakerphone and say a short phrase. Do you hear any echo? Try again using headphones on their end. Does that change anything?
Do this with a grown-up118. Why Did Sailors Blow a Horn Near Cliffs and Listen for the Echo?
Draw a harbor map with a ship, a cliff, a horn blast, and the path of the echo. Mark a delay of 2 seconds. How far is the cliff using 343 meters per second?
119. Why Does Your Voice Sound Hollow Inside a Bucket or a Big Pipe?
Speak into an empty clean bucket held in front of your face. Then try a smaller bowl and a paper tube. Which one sounds the most hollow? Which one sounds the deepest?
120. How Can Sound Waves Clean Eyeglasses?
Draw a picture of how tiny bubbles pop beside a dirty spot and push the dirt away. Label the sound waves, the water, the bubbles, and the glasses.
121. Can a Singer Really Break a Glass with Their Voice?
With a grown-up, wet your fingertip and slowly rub the rim of a clean thin glass with a little water in it. It sings! Add or pour out some water. How does the pitch change?
Do this with a grown-up122. Why Can Sound Hold Tiny Bits of Foam in Mid-Air?
Tie one end of a rope to a doorknob and shake the other end until you get a stable pattern with loops and still points. The still points are like nodes. Count the loops.
123. Why Does Sand Make Patterns on a Vibrating Plate?
Ask a teacher or a science center if you can see a Chladni plate. Meanwhile, draw the pattern you expect. Where do you think the sand will collect: at the shaking parts or the still lines?
124. Why Do Some Backing-Up Trucks Go Shh-Shh Instead of Beep-Beep?
Close your eyes while a friend hums one steady note from different spots around you. Point to the sound. Then your friend says “shhh” from the same spots. Which is easier to locate?
125. Why Can Echoes Make a Speech Hard to Understand?
Have a friend read ten random words to you in an echoey stairwell or gym and write down what you hear. Do the same in a carpeted room. In which room did you get more right?
Expedition 6: Hearing & Listening Safely (25)
126. What Do the Tiny Hair Cells in Your Ears Do, and Why Can't They Grow Back?
Brush your palm over a bristle brush. The bristles bend and spring back. If you press very hard, they bend too far and stay flat. Hair cells need gentle sounds to keep springing back.
127. Why Do People Who Work Near Loud Machines Wear Ear Protection?
Listen to a quiet TV from across a room. Then listen again while wearing winter earmuffs or a thick hat over your ears. How much quieter is it? Look for ear protection next time you see workers or mowers.
128. Why Do Ear Defenders Matter at Fireworks, Motor Races, and Loud Concerts?
Make a “loud event kit” with a grown-up: ear defenders that fit you, a spare pair, and a plan to stand far from speakers or fireworks. Practice putting them on quickly.
Do this with a grown-up129. How Can You Tell If Your Headphones Are Too Loud?
With a grown-up, find the volume limit setting on a phone or tablet. Try the arm’s length test with a friend and talk about what you find. Where is a good volume that you can still enjoy?
Do this with a grown-up130. Why Do Listening Breaks Help Your Ears?
Make a listening schedule with a grown-up: for each hour of music or videos, plan a ten-minute break for a quiet activity, like reading, drawing, or looking out the window.
Do this with a grown-up131. Why Do Your Ears Sometimes Ring After a Very Loud Noise?
Make a “what to do” card: move away from the noise, tell a grown-up, rest your ears in a quiet place, and see a doctor if the ringing lasts more than a day or your ears hurt.
Do this with a grown-up132. Why Do Hearing Tests Use Beeps in Headphones?
Play a quiet-sound game: a friend taps two fingers together softly and walks away from you. Raise your hand when you can no longer hear it. Measure the distance with steps. Try again with a different sound.
133. How Does a Hearing Aid Work?
Draw the path of sound through a hearing aid: microphone, computer, speaker, ear. Which part does the job that your outer ear does? Which does the job of a volume knob?
134. Why Do Captions on Videos Help Lots of People?
Watch one minute of a show with the sound off and captions on. How much can you follow? Then try with captions off. What did you notice about faces, actions, and words?
135. Why Do Ears Make Earwax?
Press a strip of clear sticky tape on a dusty shelf and look at what it picks up. Earwax is sticky in the same way. List three jobs that earwax does for your ears.
136. Why Shouldn't You Poke Anything Into Your Ears?
After a bath, use a soft damp washcloth to gently wipe only the outside parts of your ears. Practice saying to a grown-up: “My ear feels blocked.” Safe cleaning is for the outside only.
Do this with a grown-up137. Why Are Our Outer Ears Shaped Like Curly Funnels?
Close your eyes and have a friend snap fingers behind you at different heights. Point to the sound. Now fold your ears forward with your hands and try again. Is it harder?
138. Why Do Some Crosswalks Beep or Chirp?
With a grown-up at a crosswalk, listen for the chirps or beeps while you wait. Match each sound to the signal light. Remember: you still need to look both ways before you cross.
Do this with a grown-up139. Why Do Some Alarms Flash a Light as Well as Make a Sound?
Talk with a grown-up about where the smoke alarms are in your home, and plan two ways out of every room. A grown-up tests the alarms. Can you spot a flashing alarm anywhere?
Do this with a grown-up140. Why Does Background Noise Make It Harder to Focus?
Study ten words for one minute in a quiet room, then write what you remember. Do it again with a different ten words while a quiet radio talks. Which time did you remember more?
141. Why Is It Risky to Wear Headphones While Biking or Crossing the Street?
Stand away from the road with a grown-up and list every sound that tells you something about traffic: engines, bike bells, sirens, beeping signals. What would you miss if you were wearing headphones?
Do this with a grown-up142. Why Can Younger People Hear Some Sounds That Adults Can't?
Ask family members of different ages which everyday beeps and chirps they can hear, like a microwave beep, a smoke-alarm chirp, or a phone tone. Who hears the highest ones? Make a chart.
143. How Can You Make a Noisy Room Quieter?
With a grown-up, drag a chair across a hard floor, then stick felt pads on the legs and drag it again. How much quieter is it? What else could you do to quiet your room?
Do this with a grown-up144. What Is White Noise, and Why Does It Hide Other Sounds?
Say a long quiet “shhhh” and notice that it has no clear note. Then listen to a fan running in a room, and tap a pencil on the desk. Is the tapping less noticeable with the fan on?
145. How Do Vibrating Alarm Clocks and Flashing Doorbells Help People Who Are Deaf or Hard of Hearing?
Design an alert system for someone who cannot hear the doorbell. Draw it with at least two ways of letting them know. Which one would work best at night? Which would work best in the kitchen?
146. How Can People Who Are Deaf or Hard of Hearing Enjoy Music?
Blow up a balloon a little and hold it lightly in both hands near a speaker playing music softly with a deep beat. Can you feel the beat through the balloon? Do not pop it near your ears.
147. Why Should You Tell a Grown-Up If Your Ears Hurt or Sounds Seem Muffled?
Make a list of things to tell a grown-up about your ears: pain, feeling blocked, ringing, trouble hearing in class, or turning up the TV a lot. Practice saying them out loud.
Do this with a grown-up148. Why Do Some Toys and Kids' Headphones Have a Volume Limit?
With a grown-up, look at a headphone box or manual for a number like 85 dB. Use the loudness chart from earlier in this book. Which everyday sounds are louder than the limit?
Do this with a grown-up149. Why Do Some Animals Have Giant Ears?
Sit quietly and list every sound you hear in 30 seconds. Then hold two paper plates curved behind your ears and listen again. What is different? Draw an animal with ears built for its job.
150. What Is the Faintest Sound a Person Can Hear?
Test how far away you can hear two fingers rubbing together beside someone’s ear. Take turns with family. Everyone’s ears are a bit different, and small differences are normal.