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High and low sounds

Waves, sound and light · level 1, lesson 3 of 6

A question to start

A big dog's bark is deep and low. A tiny bird's tweet is high. Why do they sound so different?

The idea

How high or low a sound is, is called its pitch.

  • Things that shake fast make high sounds.
  • Things that shake slowly make low sounds.

Small, short or tight things usually shake fast and sound high. Big, long or loose things usually shake slowly and sound low.

lowesthighesttap each bottle with a spoon

Worked examples

1. A guitar. The thick strings play low notes; the thin strings play high notes.

2. A ruler on a table. With a long piece sticking out, it twangs low. Pull it in, so only a short piece sticks out, and it twangs higher.

3. Bottles of water. Tap bottles with different amounts of water. The glass and water shake, and the bottle with the most water gives the lowest note.

Try it

  1. What is the pitch of a sound?
  2. Does a fast shake make a high or a low sound?
  3. Which strings on a guitar make the low notes?
  4. You make the piece of ruler over the table edge shorter. Does the twang go higher or lower?
Answers
  1. How high or low it is.
  2. A high sound.
  3. The thick ones.
  4. Higher.

Common mistake

"High notes are louder." Pitch is about how fast something shakes; loudness is about how big the shakes are. You can sing a high note quietly.

Where it leads