The** vibration** one observes in a guitar string, once it has been plucked, is the** sum** of an infinity of stationary waves called ** harmonics**, or **modes of vibration**.

The **tension**, adjusted by the tuning pegs, and the** length** of the string, impose upon the waves that are propagated certain conditions of **frequency** and **wavelength**.

The two extremities of the string define **limiting conditions**, which impose zero displacement at these points, at all times.

This simulation enables us to observe the first four harmonics **separately**, which is not possible in reality.

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The stationary wave that has the **greatest wavelength**, and is in accord with the limiting conditions, is the first harmonic.

It is also called the** fundamental**.

It has **two nodes of vibration** at the two extremities and a **single antinode** in the middle, which gives it this very characteristic bulging** envelope** shape.

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Its **resonant **frequency , noted as f_{0} depends on the length of the string: the **shorter **the string, the** higher** the frequency is, and the **higher the pitch** of the sound is.

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A harmonic of rank “n” is a stationary wave with a frequency n times the frequency of the fundamental.

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However, even if the series of harmonics is **infinite**, their respective **amplitudes** decrease very rapidly, and only the first harmonics, among which is the fundamental, are perceived by our ears.