Sound Wave
Light, Sound and Waves

Listening to music with a new ear

Classroom Activity for 11-14 Supporting Physics Teaching

What the Activity is for

Discussing a variety of sounds.

When teaching about sound it is fairly common practice to listen to musical instruments, or music of some kind, perhaps from an electronic keyboard. Here we show you how to deal with this variety of sounds, without having to discuss the differently shaped wiggly lines that appear on oscilloscope screens. In fact we point to something altogether more fundamental – the combination of the different frequencies in varying proportions, which create the soundscapes that we enjoy.

What to Prepare

  • a variety of musical instruments
  • software, plus computer and microphone, that allows you to look at different frequencies as they are played

What Happens During this Activity

Set up the software and hardware so that they show the frequencies present in any note as it is played. You'll need to experiment with the software that you choose, and probably read the manual. A plot of frequency against time is the target (such displays are often called spectrograms or spectrographs).

If practised, a useful first step is to whistle into the set-up, with a steadily increasing pitch. You should aim to produce a steady increase in frequency, consisting of a narrow band of frequencies: nearly a pure note. Use a spectrograph style display, with frequency plotted upwards and time scrolling along to explain how loudness and pitch show up on the screen.

Treat this as a familiarisation exercise.

When a particularly interesting trace is on the screen, freeze it. Point out the dominant frequency, often shown by being brightest, and the mixture of other frequencies present. Say that these are an important aspect of the way we identify the sound as coming from a particular instrument. Compare a number of instruments.

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