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A waveform is the shape of a wave. Below is a graph of a waveform for a sound wave created by a clarinet. Sound waves are created by changes in pressure

waveform for sound waves
Sound waves created by a clarinet. [Image source: Rburtonresearch – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=45035734]

of a medium such as air. The horizontal axis shows the passage of time in tiny fractions of a second. The vertical axis shows air pressure. Atmospheric air pressure which would prevail if there were no sound at all is indicated by 0, in the middle of the vertical axis. Different pitches are created as the air pressure increases and decreases.


waveforms schematic
[Image source: By Omegatron – Own work, https://commons.wikimedia.org/w/index.php?curid=343520. Retrieved from https://en.wikipedia.org/wiki/Wave Retrieved Sept. 21, 2017]

Some waveforms flow smoothly and others, when graphed, take more angular or jagged forms, as in the diagram to the right. Again, time runs across the horizontal axis and some phenomenon, let’s say the intensity of a light, runs vertically. Consider the square waveform, the green line, for example. It shows that the light intensity remains at a high level for a bit of time, virtually instantaneously drops to a low level for the same amount of time, virtually instantaneously returns to its high level for the same amount of time, drops…etc.

wave three-dimensional
A 3-dimensional wave with 6 peaks.

Physical waves are three-dimensional as they travel through time. Physical waves are not changes in a single dimension such as pressure or intensity, as shown on the prior graphs. The accompanying diagram shows a three-dimensional wave. In this still image, we see the wave cresting in six peaks. Were we to continue watching, we would see the peaks dissolve and, in their stead, troughs would form. In our three-dimensional world, waveforms are really three-dimensional. But, sometimes, it’s desirable to abstract a single dimension like air pressure or light intensity and graph this single dimension against time.

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