Oscillators: waveforms, pitch and noise

Draw two cycles of each waveform on its axes.

Draw with a finger or the mouse. Then show the answers over your drawings to check them.

Check each one: two whole cycles, centred on the line, with the right corners. A sawtooth drawn the other way round (a sudden rise, then a ramp down) is right too.

Name the four shapes

Say it in words

Tick each point your words or drawings make.

• An oscillator makes the raw sound: a wave that repeats. The other parts of a synth shape it.
• Sine: one harmonic, the fundamental only: pure and smooth.
• Triangle: odd harmonics (1, 3, 5…), weak ones: soft, like a flute.
• Square: odd harmonics only, stronger: hollow, like a clarinet.
• Sawtooth: every harmonic (1, 2, 3…): the brightest, buzzy.
• More harmonics, and stronger ones, make a brighter tone.
• Frequency sets the pitch: double it for an octave up (220 Hz to 440 Hz), halve it for an octave down.
• Period = 1 ÷ frequency: 220 Hz takes about 4.5 ms a cycle, 440 Hz about 2.3 ms.
• Noise is random: nothing repeats, so it has no pitch. It has every frequency at once (hi-hats, snares, wind).
• Drawings: two whole cycles, centred on the line; sine round, triangle sharp, square flat with straight sides, sawtooth a ramp and a drop.