Other waveform properties

In addition to frequency, other properties of sound waves include amplitude, wavelength, period, and phase.

Figure. Waveform properties, showing wavelength and amplitude.

Amplitude: The amplitude of a waveform indicates the amount of air pressure change. It can be measured as the maximum vertical distance from zero air pressure, or “silence” (shown as a horizontal line at 0 dB in the illustration). Put another way, amplitude is the distance between the horizontal axis and the top of the waveform peak, or the bottom of the waveform trough.
Wavelength: The wavelength is the distance between repeating cycles of a waveform of a given frequency. The higher the frequency, the shorter the wavelength.
Period: The wave period is the amount of time it takes to complete one full revolution of a waveform cycle. The higher and faster the frequency, the shorter the wave period.
Phase: Phase compares the timing between waveforms and is measured in degrees—from 0 to 360.
When two waveforms begin at the same time, they are said to be in phase or phase-aligned. When a waveform is slightly delayed in comparison to another waveform, the waveforms are said to be out of phase.
Note: It is difficult to discern a constant phase difference over the entire wave period, but if the phase of one of the waveforms changes over time, it becomes audible. This is what happens in common audio effects such as flanging and phase shifting.
When you play two otherwise identical sounds out of phase, some frequency components—harmonics—can cancel each other out, thereby producing silence in those areas. This is known as phase cancelation, and it occurs where the same frequencies intersect at the same level.

Fourier theorem and harmonics

According to the Fourier theorem, every periodic wave can be seen as the sum of sine waves with certain wave lengths and amplitudes, the wave lengths of which have harmonic relationships—that is, ratios of small numbers. Translated into more musical terms, this means that any tone with a certain pitch can be regarded as a mix of sine tones consisting of the fundamental tone and its harmonics, or overtones. For example, the basic oscillation—the fundamental tone or first harmonic—is an “A” at 220 Hz, the second harmonic has double the frequency (440 Hz), the third harmonic oscillates three times as fast (660 Hz), the next harmonics four and five times as fast, and so on.

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MainStage User Guide: PDF

MainStage Instruments: PDF

MainStage Effects: PDF

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