Sound Wave
Light, Sound and Waves

Whistling waveforms

Practical Activity for 11-14 14-16 IOP RESOURCES

Students download an oscilloscope app onto their phones to investigate pitch and loudness of sounds.


Each student will need:

  • A smartphone
  • Two different sized bottles with long necks (optional)


Students will need download an oscilloscope app with a pause function.. For example, they could use Oscilloscope (xyz apps) from the Play store (tap screen to stop trace) or Oscilyzer from the App Store (use pause button to stop trace).


Ask students to:

  1. Download the oscilloscope app on to their phone.
  2. Whistle and observe the trace on the screen. If they can’t whistle, blow over a bottle to make a sound.
  3. Whistle a loud, steady note pause the trace. If they missed it, repeat to try to catch the waveform mid-whistle.
  4. Repeat, but this time whistle more quietly.
  5. Whistle with a high pitch and then a low pitch.

Discussion prompts

  • How does the waveform change with loudness?
  • How does the waveform change with pitch?

Teaching notes

If students can’t whistle, they can blow over bottles or use a musical instrument such as a guitar or a recorder. They should see that when the sound is louder the peaks of the waveform are bigger, and that when the pitch is higher the peaks are closer together.

Learning outcome

Students sketch waveforms for sounds with different volumes and frequencies.

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