Chapter 5 of 8

All 8 chapters
  1. 1Sounds come from vibrations, readunderstood
  2. 2Sound travels, readunderstood
  3. 3Echoes, readunderstood
  4. 4A string telephone, readunderstood
  5. 5Loud and quiet, readunderstood
  6. 6High and low notes, readunderstood
  7. 7How we hear, readunderstood
  8. 8Noise and our ears, readunderstood

S2.7.5 Chapter 5

Loud and quiet

Why is a shout louder than a whisper?

Your guess

Pick one before you read on. It is fine to be wrong.

Your guess

  • You picked A. Read on. At the end, the chapter comes back to your guess.

  • You picked B. Read on. At the end, the chapter comes back to your guess.

  • You picked C. Read on. At the end, the chapter comes back to your guess.

  • You picked D. Read on. At the end, the chapter comes back to your guess.

By the end you can

  • Explain that bigger vibrations make louder sounds
  • Explain why a sound gets quieter as you move away from it

Hit a drum softly. The skin moves a little. Hit it hard. The skin moves a lot.

A bigger move makes a louder sound. The volume of a sound is how loud or quiet it is.

See it three ways

As a picture

Two pictures of a rubber band and its sound wave. The top wave is short and is labelled quiet. The bottom wave is tall and is labelled loud. Both waves have the same number of bumps.quietloud

In words

A small vibration makes a short wave and a quiet sound. A big vibration makes a tall wave and a loud sound. The number of bumps is the same.

Pluck a rubber band gently. It moves a little, and the sound is quiet. Pluck it harder. It moves further, and the sound is louder.

Two rubber bands, each stretched between two posts. The top band has a soft pluck, labelled soft pluck. Its dashed lines bend only a little, labelled small vibration. The bottom band has a hard pluck, labelled hard pluck. Its dashed lines bend a lot, labelled big vibration.soft plucksmall vibrationhard pluckbig vibration
A hard pluck makes a big vibration and a loud sound.

The sound is not higher or lower. It is only louder. The size of the move changes the volume, not the note.

Now think about distance. A bell rings. Close to it, the sound is loud. Far away, it is quiet. Why?

The sound spreads out as it goes. Think of ripples on a pond. They grow into bigger rings, and the rings get weaker.

Draw it first

Draw how a sound spreads out

  1. A circle on the left, labelled source. Five arrows spread out from it to the right. A short line crossing the arrows near the source is labelled near. A long line crossing the arrows far from the source is labelled far.source

    1 Draw a circle for the thing that makes the sound. Write source.

  2. A circle on the left, labelled source. Five arrows spread out from it to the right. A short line crossing the arrows near the source is labelled near. A long line crossing the arrows far from the source is labelled far.source

    2 Draw five arrows that spread out from it.

  3. A circle on the left, labelled source. Five arrows spread out from it to the right. A short line crossing the arrows near the source is labelled near. A long line crossing the arrows far from the source is labelled far.sourcenearfar

    3 Draw a short line near the source. Draw a long line far away. Write near and far.

Near the source, the sound meets a short line. Far away, the same sound meets a long line.

The sound is shared over more space. So each part of that space gets less. The sound is quieter.

Air takes in a little sound as it goes. Soft things take in sound too. Cloth and grass take in more than a hard wall.

Try it

Hard pluck, soft pluck, and walking away

You need: a rubber band, a small open box, or a tin with no sharp edges, a friend, two spoons, open ground, or a long room.

Be safe: Keep the box away from your face. Pull the band only a little. Tap the spoons gently, away from your face.

  1. Stretch the rubber band across the open top of the box.
  2. Hold the box away from your face. Pluck the band softly.
  3. Watch how far the band moves. Listen.
  4. Now pluck it hard. Watch and listen again.
  5. Your friend taps the two spoons together, the same way each time.
  6. Walk away one step at a time. Stop when the taps are very quiet. Count your steps.

What you will see: A hard pluck moves the band further, and the sound is louder. The note stays the same. The taps get quieter with every step you take away. The step counts in the table are only an example.

If you cannot try it, this is what happens.
Two tables. The first table has the headings Pluck, Band moves and Sound. Its rows are: soft, a little, quiet; and hard, a lot, loud. The second table has the headings Steps away and You hear. Its rows are: 1, loud; 5, quiet; 15, very quiet.PluckBand movesSoundsofta littlequietharda lotloudSteps awayYou hear1loud5quiet15very quiet

A wrong idea many people have

A louder sound is a higher note.

Why it feels right: We say we raise our voice to be louder. To raise is to go up, like a high note.

The test that breaks it: Hum one steady note with a hand on your throat. Hum the same note again, louder. Your throat shakes more, but the note is the same. Or pluck the rubber band softly, then hard. It sounds louder, not higher.

What is true: Bigger vibrations make a louder sound. The note stays the same.

Key words

volume
how loud or quiet a sound is.

Back to your guess

The answer is D: The voice box shakes more, with bigger moves.

A shout shakes the voice box with bigger moves. A bigger vibration makes a louder sound.

Check yourself

Try each one before you look. A wrong answer tells you where to go next.

  1. Kofi plucks a rubber band hard. How is this different from a soft pluck?

    Tap your answer.

    1. Not this one. A louder sound comes from a bigger move. The band moves further. Try another.

    2. Not this one. A hard pluck makes a bigger move, not a higher note. The note stays the same. Try another.

    3. Not this one. A bigger move does not make a lower note. The note stays the same. Try another.

    4. Yes, that is right. A bigger vibration makes a louder sound.

    See the answer

    The band moves further, and the sound is louder.

    A bigger vibration makes a louder sound.

    • If you chose A: A louder sound comes from a bigger move. The band moves further.
    • If you chose B: A hard pluck makes a bigger move, not a higher note. The note stays the same.
    • If you chose C: A bigger move does not make a lower note. The note stays the same.

  2. Look at the picture. Which rubber band makes the louder sound?

    Two pictures, P and Q. Each shows a rubber band and its sound wave. In P the wave is tall. In Q the wave is short. Labels: P, Q.PQ
    Tap your answer.

    1. Not this one. Both waves have the same number of bumps. But P is taller. Its vibration is bigger, so it is louder. Try another.

    2. Yes, that is right. P has the tall wave. A tall wave is a big vibration, so the sound is louder.

    3. Not this one. Q has a short wave. A short wave is a small vibration and a quiet sound. Try another.

    See the answer

    Band P

    P has the tall wave. A tall wave is a big vibration, so the sound is louder.

    • If you chose A: Both waves have the same number of bumps. But P is taller. Its vibration is bigger, so it is louder.
    • If you chose C: Q has a short wave. A short wave is a small vibration and a quiet sound.

  3. Ana walks away from a ringing bell. Why does it get quieter?

    Tap your answer.

    1. Yes, that is right. The same sound is shared over more space. Each part gets less.

    2. Not this one. The bell rings the same. Ana moved, so the sound she gets is smaller. Try another.

    3. Not this one. The note stays the same. Only the volume gets smaller. Try another.

    See the answer

    The sound spreads out over a bigger space.

    The same sound is shared over more space. Each part gets less.

    • If you chose B: The bell rings the same. Ana moved, so the sound she gets is smaller.
    • If you chose C: The note stays the same. Only the volume gets smaller.

  4. Lucía plucks a rubber band softly, then hard. What stays the same?

    Tap your answer.

    1. Not this one. The hard pluck is louder, so the volume changes. Try another.

    2. Not this one. A hard pluck moves the band further. That is why it is louder. Try another.

    3. Yes, that is right. The size of the move changes the volume. It does not change the note.

    See the answer

    The note

    The size of the move changes the volume. It does not change the note.

    • If you chose A: The hard pluck is louder, so the volume changes.
    • If you chose B: A hard pluck moves the band further. That is why it is louder.

  5. From an earlier chapter

    Amina hums and touches her throat. What does she feel?

    Tap your answer.

    1. Not this one. Every sound comes from something that vibrates. Her throat shakes when she hums. Go to S2.7.1. Try another.

    2. Yes, that is right. Her voice box vibrates when she hums. That vibration makes the sound.

    3. Not this one. Air alone does not buzz. The buzz is the voice box shaking. Go to S2.7.1. Try another.

    See the answer

    Her throat shaking

    Her voice box vibrates when she hums. That vibration makes the sound.

    • If you chose A: Every sound comes from something that vibrates. Her throat shakes when she hums. Go to S2.7.1.
    • If you chose C: Air alone does not buzz. The buzz is the voice box shaking. Go to S2.7.1.

  6. Draw two sound waves from one rubber band. One is quiet. One is loud.

    See the answer

    The quiet wave is short. The loud wave is tall. Both have the same number of bumps.

    A bigger vibration makes a taller wave and a louder sound. The note does not change.

  7. Look at the picture. Sipho and Leila hear the same bell. Who hears it louder?

    A circle on the left is a bell, labelled bell. Two people stand to its right, labelled Sipho and Leila. A dashed line from the bell to Sipho is labelled 2 m. A longer dashed line from the bell to Leila is labelled 20 m. Labels: bell, Sipho, Leila, 2 m, 20 m.bellSiphoLeila2 m20 m
    Tap your answer.

    1. Yes, that is right. Sipho is nearer. The sound is shared over less space there, so it is louder.

    2. Not this one. The bell rings the same, but the sound spreads out. Each part of it gets weaker with distance. Try another.

    3. Not this one. The sound does not grow. It spreads over more space, so each part gets less. Try another.

    See the answer

    Sipho, because the sound has not spread out as far.

    Sipho is nearer. The sound is shared over less space there, so it is louder.

    • If you chose B: The bell rings the same, but the sound spreads out. Each part of it gets weaker with distance.
    • If you chose C: The sound does not grow. It spreads over more space, so each part gets less.

  8. Hana plucks a rubber band gently. How can she make a louder sound with the same band?

    Tap your answer.

    1. Not this one. Plucking more often does not make one sound louder. A harder pluck does. Try another.

    2. Not this one. A tighter band shakes faster. That changes the note, not the volume. Try another.

    3. Yes, that is right. A harder pluck makes a bigger vibration. A bigger vibration makes a louder sound.

    See the answer

    Pluck it harder.

    A harder pluck makes a bigger vibration. A bigger vibration makes a louder sound.

    • If you chose A: Plucking more often does not make one sound louder. A harder pluck does.
    • If you chose B: A tighter band shakes faster. That changes the note, not the volume.

Keep it

Copy this into your exercise book.

A bigger vibration makes a louder sound. The note stays the same. A sound gets quieter as you walk away. It spreads out over a bigger space.

Draw: A short wave and a tall wave. Write quiet and loud.

Reading with a child? A short page for the adult: what this chapter teaches and three questions to ask.

No internet tomorrow? Save the whole book as one file (610 KB). It opens on any phone.