Moog-music MF-102 Ring Modulator User Manual download pdf (Page 5)

HOW A RING MODULATOR WORKS

Let's start with some definitions. Please read this section carefully, as it will help you to

understand the basic ideas underlying ring modulation.

Sound is a vibration of the air. The speed of vibration is called the frequency. It is

measured in Hertz (Hz). One Hz is one vibration per second. We hear vibrations from 20

Hz to 20,000 Hz.

Musical sounds generally have many frequency components. They're called

harmonics, or overtones, or partials. They are what give the sound its characteristic tone

color, or timbre. We can represent a musical sound either as a waveform or as a

spectrum. The waveform is a time graph of the actual shape of the vibration, while the

spectrum shows how strong each of the sound's harmonics is. See Figure 3.

Figure 3 - A musical sound can be represented as a waveform (top graph) or as a spectrum (bottom graph).

The waveform of a single harmonic is called a sine wave. The spectrum of a sine

wave is just a single line. Figure 4 shows the waveform and spectrum of a 500 Hz sine

wave, while Figure 5 shows the waveform and spectrum of a 100 Hz sine wave. If you

listen to a 500 Hz sine wave, you hear a pitch nearly an octave above middle C, with a

mellow, muted quality, like a flute or a whistle. A 100 Hz sine wave also sounds mellow

and muted, but its pitch is more than an octave below middle C.

Figure 4 - Waveform and spectrum of a 500 Hz. sine wave. Figure 5 - Waveform and spectrum of a 100 Hz sine

wave.

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Moog-music MF-102 Ring Modulator User Manual Page 5