Building up sounds

What the Activity is for

Exploring a combination of frequencies.

Few sounds consist of a pure tone of just one frequency. Here we show how different frequencies can be heard at once, at the same time as showing a representation of the motion of the vibrator making these noises (but slowed down a little!)

What to Prepare

• a computer in the classroom, driving speakers loud enough for the class to hear, together with a data projector and a large screen
• a copy of the interactive (see below)

What Happens During this Activity

Start with the simple tones, then play the more complex sounds. Draw attention to what the on-screen loudspeaker is doing. So that pupils can see this, it is 1000 times slower than the loudspeakers actually making the noise.

Say that we can make up any sound we like by combining the right balance of appropriate frequencies: a bit of 200 Hz, a lot of 1000 Hz and a lot of 3500 Hz make an interesting note.

Combining different amplitudes of chosen frequencies is how synthesisers work. As we said before, you can get a long way in sound building on amplitude and frequency.

For the more adventurous, many sound processing packages allow you add frequencies to your heart's content.