PURPOSE: To demonstrate Fourier synthesis of complex wave shapes.

DESCRIPTION: Complex waves may be formed using up to twelve harmonics with independently variable amplitudes and phases. Any individual harmonic such as the fundamental (in the photograph above) can be shown on one trace of the oscilloscope, wh ile the sum is shown on the other trace. The wave can be simultaneously seen on the oscilloscope and heard using a loudspeaker with a separate volume control. Digital phase locking of all harmonics allows the frequency to be varied from below 100 Hz to above 1000 Hz while the wave shapes remain fixed, to show that timbre is primarily dependent on harmonic structure, and not on frequency or intensity. Some easily produceable wave shapes are square wave, sawtooth wave, triangular wave and pulse train.

SUGGESTIONS: Practice for most effective use.

REFERENCES: (PIRA 3C50.00) See Demonstration Reference File for information on use of the synthesizer as well as construction circuits and drawings.

EQUIPMENT: Fourier synthesizer, four-trace oscilloscope, and loudspeaker on scope/TV cart, as photographed.

SETUP TIME: 5 min.

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