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Unit 6: Sound, the Earth and eclipses

Sound waves — HIA International - Grade 6 Revision Notes & Topical Questions

5 min read 8 parts Lesson 2 of 7 3 quizzes

📚 HIA International - Grade 6 Hub / Topical Revision
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Lesson summary

6.1 Sound waves — HIA INTERNATIONAL notes: Explain that sound comes from vibrations, how particles vibrate in a sound wave and why sound does not travel in a vacuum.Vibrate — to move backwards and forwards very quicklySound source — things that vibrate make sounds, such as a drum…

  • Energy transfer
  • Very loud sounds
  • Very quiet sounds
  • High pitch
  • Solids, liquids and gases
  • To hear a sound

Part 1 of 6Sound from vibrations

Vibrate
  • Vibrate to move backwards and forwards very quickly
Sound source
  • Sound source things that vibrate make sounds, such as a drum, vocal cords or the paper cone of a loudspeaker
Loudness
  • Loudness hitting a drum harder makes it vibrate more, giving a louder sound
Pitch
  • Pitch sounds vary in loudness and pitch, from low-pitched thunder to a high-pitched crying baby

Part 2 of 6How a sound wave travels

1
An object vibrates backwards and forwards.
2
Each forward vibration pushes the air in front of it forward.
3
The air particles vibrate backwards and forwards in time with the object.
4
These particles make the particles in front of them vibrate, which makes a sound wave.
  • Speed
    • the speed of sound in air is about 343 metres per second

Part 3 of 6Sound energy

Energy transfer
  • Energy transfer sound waves transfer sound energy, and the vibration is transferred to other objects which start to vibrate
Very loud sounds
  • Very loud sounds can damage the ears
Very quiet sounds
  • Very quiet sounds the vibrations may be too small for the ears to detect
High pitch
  • High pitch a sound at a certain pitch can break objects such as glass

Part 4 of 6Sound in different media

1Medium
  • Medium the substance a sound wave moves through
2Solids, liquids and gases
  • Solids, liquids and gases sound travels through anything that has particles, moving the same way in each
  • Tapping a table and listening with an ear on the table shows sound travels through a solid.
  • Whales and dolphins communicate with sound in water.

Part 5 of 6Sound in a vacuum

To hear a sound
  • To hear a sound there must be a vibration and a medium containing particles
Vacuum
  • Vacuum a space with no particles, so nothing vibrates to make a sound wave
Space
  • Space space is a vacuum, so sound does not travel through it
Bell jar demonstration
  • Bell jar demonstration an electric bell in a jar is heard until the air is pumped out, after which the bell is seen vibrating but cannot be heard

Part 6 of 6Modelling a sound wave

Slinky spring
  • Slinky spring moving one end backwards and forwards makes a wave that travels along the spring
Marks on the spring
  • Marks on the spring represent particles, which move backwards and forwards while the wave travels forward

Key terms

TermMeaning
VibrateMove backwards and forwards very quickly.
Sound waveVibration of particles that carries sound from a source.
MediumThe substance a wave moves through.
VacuumA space with no particles.
PitchHow high or low a sound is.
LoudnessHow loud or quiet a sound is.

Avoid these mistakes

1
Saying sound travels in a vacuum — there are no particles to vibrate
2
Saying air particles travel from the source to the ear — they only vibrate backwards and forwards
3
Mixing up pitch and loudness — loudness depends on how much the object vibrates, pitch is how high or low
4
Saying sound only travels through air — it travels through solids, liquids and gases

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