Editing String instrument (section)

=== Acoustic instruments ===
{{See also|Musical acoustics}}
[[File:Chordophone (Cordophone).jpg|thumb|The Moroccan [[gimbri|loutar]] uses a soundboard made of goatskin.]]

A vibrating string strung on a very thick log, as a hypothetical example, would make only a very quiet sound, so string instruments are usually constructed in such a way that the vibrating string is coupled to a hollow resonating chamber, a [[soundboard (music)|soundboard]], or both. On the violin, for example, the four strings pass over a thin wooden bridge resting on a hollow box (the body of the violin). The normal force applied to the body from the strings is supported in part by a small cylinder of wood called the [[soundpost]]. The violin body also has two "f-holes" carved on the top. The strings' vibrations are distributed via the bridge and soundpost to all surfaces of the instrument, and are thus made louder by matching of the [[acoustic impedance]]. The correct technical explanation is that they allow a better match to the [[acoustic impedance]] of the air.{{citation needed|date=October 2019}}

It is sometimes said that the sounding board or soundbox "amplifies" the sound of the strings. In reality, no power amplification occurs, because all of the [[energy]] to produce [[sound]] comes from the vibrating string. The mechanism is that the sounding board of the instrument provides a larger surface area to create [[sound wave]]s than that of the string and therefore acts as a matching element between the acoustic impedance of the string and that of the surrounding air. A larger vibrating surface can sometimes produce better matching; especially at lower frequencies.

All [[lute]]-type instruments traditionally have a bridge, which holds the string at the proper action height from the fret/finger board at one end of the strings. On acoustic instruments, the bridge performs an equally important function of transmitting string energy into the "sound box" of the instrument, thereby increasing the sound volume. The specific design, and materials used in the construction of the bridge of an instrument, have a dramatic impact upon both the sound and responsiveness of the instrument.

Achieving a tonal characteristic that is effective and pleasing to the player's and listener's ear is something of an art and craft, as well as a science, and the makers of string instruments often seek very high quality woods to this end, particularly [[spruce]] (chosen for its lightness, strength and flexibility) and [[maple]] (a very hard wood). Spruce is used for the sounding boards of instruments from the violin to the piano. Instruments such as the banjo use a drum, covered in natural or synthetic skin, as their soundboard.

Acoustic instruments can also be made of artificial materials, such as [[carbon fiber]] and [[fiberglass]] (particularly the larger, lower-pitched instruments, such as cellos and basses).

In the early 20th century, the [[Stroh violin]] used a diaphragm-type [[resonator]] and a metal horn to project the string sound, much like early mechanical gramophones. Its use declined beginning about 1920, as electronic amplification through [[power amplifier]]s and [[loudspeaker]]s was developed and came into use. String instrument players can electronically amplify their instruments by connecting them to a [[PA system]] or a [[guitar amplifier]].