Acoustics / Electroacoustics
The pattern of SOUND PRESSURE variation, usually displayed as a two-dimensional graph of pressure or AMPLITUDE against time (see OSCILLOSCOPE). For PERIODIC waveforms, a single CYCLE or PERIOD defines the waveform. Also called sound pressure function, particularly when represented digitally.
The simplest waveform is the SINE WAVE, since it has only one FREQUENCY associated with it. More complex waveforms can be constructed from sine waves of various frequencies by the LAW OF SUPERPOSITION. Common waveforms used in SOUND SYNTHESIS are the TRIANGLE WAVE, SQUARE WAVE, SAWTOOTH WAVE and PULSE WAVE. These AUDIO waveforms are often termed fixed waveforms because of their lack of variation, whereas acoustic waveforms are constantly varying.
The waveform represents the behaviour of the sound in the time domain, and since its shape is indicative of the frequency content of the sound, waveform is sometimes used synonymously with TIMBRE, although all contributing factors to timbre cannot be understood simply in terms of the waveform. See discussion under SPECTRUM, TIMBRE.
See also: DISTORTION, FOURIER ANALYSIS, LAW OF SUPERPOSITION, MODULATION, OSCILLATOR, PEAK CLIPPING, RECTIFICATION, TRANSIENT. Compare: ENVELOPE.
Sound Example: Sine wave at 100 Hz.Sound Example: Sawtooth wave at 100 Hz.
Sound Example: Square wave at 100 Hz.
Sound Example: Triangle wave at 100 Hz.
Sound Example: Pulse wave with a 1:4 duty cycle.