# Acoustic guitar

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 String instrument Auditorium shaped guitar by C.F. Martin 321.322 (Composite Chordophone) 13th century Fast (a standard tuned guitar)

An acoustic guitar is a musical instrument in the guitar family, that projects the sounds of its vibrating strings acoustically through the air. Originally just called a guitar, the retronym 'acoustic guitar' came in use to distinguish it from an electric guitar, that relies on an electronic amplification system. The sound waves from the strings of an acoustic guitar resonate through the instrument's body, amplifying the sound. Typically, a guitar's body is a sound box, of which the top side serves as a sound board that enhances the vibration sounds of the strings. In standard tuning the guitar's six strings are tuned (low to high) E2 A2 D3 G3 B3 E4.

## Contents

Guitar strings may be plucked individually with a pick or fingertip, or strummed to play chords. Plucking a string causes it to vibrate at a fundamental pitch determined by the string's length, mass, and tension. (Overtones are also present, closely related to harmonics of the fundamental pitch.) The string causes the soundboard and the air enclosed by the sound box to vibrate. As these have their own resonances, they amplify some overtones more strongly than others, affecting the timbre of the resulting sound.

## History

The guitar is an ancient instrument, whose history can be traced back over 4000 years. Many theories have been advanced about the instrument's ancestry, but the modern acoustic guitar comes from a long progression of stringed musical instruments. It has often been claimed that the guitar is a development of the medieval instrument vihuela, which evolved from the ancient lute.

Gitterns, (small, plucked guitars) were the first small, guitar-like instruments created during the Spanish Middle Ages with a round back, like that of the lute. [1] Modern guitar-shaped instruments were not seen until the Renaissance era, when the body and size began to take a guitar-like shape.

The earliest string instruments that related to the guitar and its structure were broadly known as the vihuelas within Spanish musical culture. Vihuelas were string instruments that were commonly seen in the 16th century during the Renaissance. Later, Spanish writers distinguished these instruments into two categories of vihuelas. The vihuela de arco was an instrument that mimicked the violin, and the vihuela de penola was played with a plectrum or by hand. When it was played by hand it was known as the vihuela de mano. Vihuela de mano shared extreme similarities with the Renaissance guitar as it used hand movement at the sound hole or sound chamber of the instrument to create music. [2]

By 1790 only six-course vihuela guitars (six unison-tuned pairs of strings) were being created and had become the main type and model of guitar used in Spain. Most of the older 5-course guitars were still in use but were also being modified to a six-coursed acoustical guitar. Fernando Ferandiere's [3] book Arte de tocar la guitarra espanola por musica (Madrid, 1799) describes the standard Spanish guitar from his time as an instrument with seventeen frets and six courses with the first two 'gut' strings tuned in unison called the terceras and the tuning named to 'G' of the two strings. The acoustic guitar at this time began to take the shape familiar in the modern acoustic guitar. The coursed pairs of strings eventually became less common in favor of single strings. [4]

Finally, circa 1850, the form and structure of the modern Guitar is credited to Spanish guitar maker Antonio Torres Jurado, who increased the size of the guitar body, altered its proportions, and made use of fan bracing, which first appeared in guitars made by Francisco Sanguino in the late 18th century. The bracing pattern [5] , which refers to the internal pattern of wood reinforcements used to secure the guitar's top and back to prevent the instrument from collapsing under tension, is an important factor in how the guitar sounds. Torres' design greatly improved the volume, tone, and projection of the instrument, and it has remained essentially unchanged since.

## Acoustic properties

The acoustic guitar's soundboard, or top, also has a strong effect on the loudness of the guitar. Woods that are good at transmitting sound, like spruce, are commonly used for the soundboard. [6] No amplification occurs in this process, because musicians add no external energy to increase the loudness of the sound (as would be the case with an electronic amplifier). All the energy is provided by the plucking of the string. Without a soundboard, however, the string would just "cut" through the air without moving it much. The soundboard increases the surface of the vibrating area in a process called mechanical impedance matching. The soundboard can move the air much more easily than the string alone, because it is large and flat. This increases the entire system's energy transfer efficiency, and musicians emit a much louder sound.

In addition, the acoustic guitar has a hollow body, and an additional coupling and resonance effect increases the efficiency of energy transmission in lower frequencies. The air in a guitar's cavity resonates with the vibrational modes of the string and soundboard. At low frequencies, which depend on the size of the box, the chamber acts like a Helmholtz resonator, increasing or decreasing the volume of the sound again depending on whether the air in the box moves in phase or out of phase with the strings. When in phase, the sound increases by about 3 decibels. In opposing phase, it decreases about 3 decibels. [7] As a Helmholtz resonator, the air at the opening is vibrating in or out of phase with the air in the box and in or out of phase with the strings. These resonance interactions attenuate or amplify the sound at different frequencies, boosting or damping various harmonic tones. Ultimately, the cavity air vibrations couple to the outside air through the sound hole, [8] though some[ which? ] variants of the acoustic guitar omit this hole, or have ${\displaystyle f}$ holes, like a violin family instrument (a trait found in some electric guitars such as the ES-335 and ES-175 models from Gibson). This coupling is most efficient because here the impedance matching is perfect: it is air pushing air.

A guitar has several sound coupling modes: string to soundboard, soundboard to cavity air, and both soundboard and cavity air to outside air. The back of the guitar also vibrates to some degree, driven by air in the cavity and mechanical coupling to the rest of the guitar. The guitar—as an acoustic system—colors the sound by the way it generates and emphasizes harmonics, and how it couples this energy to the surrounding air (which ultimately is what we perceive as loudness). Improved coupling, however, comes costing decay time, since the string's energy is more efficiently transmitted. Solid body electric guitars (with no soundboard at all) produce very low volume, but tend to have long sustain.

All these complex air coupling interactions, and the resonant properties of the panels themselves, are a key reason that different guitars have different tonal qualities. The sound is a complex mixture of harmonics that give the guitar its distinctive sound.

## Amplification

Classical gut-string guitars lacked adequate projection, and were unable to displace banjos until innovations introduced helped to increase their volume. Two important innovations were introduced by US firm C.F. Martin: the steel strings and the increasing of the guitar top area; the popularity of Martin's larger "dreadnought" body size amongst acoustic performers is related to the greater sound volume produced. These innovations allowed guitars to compete with and often displace the banjos that had previously dominated jazz bands. The steel-strings increased tension on the neck; for stability, Martin[ disputed ] reinforced the neck with a steel truss rod, which became standard in later steel-string guitars. [10]

An acoustic guitar can be amplified by using various types of pickups or microphones. However, amplification of acoustic guitars had many problems with audio feedback. In the 1960s, Ovation's parabolic bowls dramatically reduced feedback, allowing greater amplification of acoustic guitars. [11] In the 1970s, Ovation developed thinner sound-boards with carbon-based composites laminating a thin layer of birch, in its Adamas model, which has been viewed as one of the most radical designs in the history of acoustic guitars. The Adamas model dissipated the sound-hole of the traditional soundboard among 22 small sound-holes in the upper chamber of the guitar, yielding greater volume and further reducing feedback during amplification. [11] Another method for reducing feedback is to fit a rubber or plastic disc into the sound hole.

The most common type of pickups used for acoustic guitar amplification are piezo and magnetic pickups. Piezo pickups are generally mounted under the bridge saddle of the acoustic guitar and can be plugged into a mixer or amplifier. A Piezo pickup made by Baldwin was incorporated in the body of Ovation guitars, rather than attached by drilling through the body; [12] the combination of the Piezo pickup and parabolic ("roundback") body helped Ovation succeed in the market during the 1970s. [11]

Magnetic pickups on acoustic guitars are generally mounted in the sound hole, and are similar to those in electric guitars. An acoustic guitar with pickups for electrical amplification is called an acoustic-electric guitar.

In the 2000s, manufacturers introduced new types of pickups to try to amplify the full sound of these instruments. This includes body sensors, and systems that include an internal microphone along with body sensors or under-the-saddle pickups.

## Types

Historical and modern acoustic guitars are extremely varied in their design and construction, far more so than electric guitars. Some of the most important varieties are the classical guitar (Spanish Guitar/Nylon-stringed), steel-string acoustic guitar and lap steel guitar.

### Body shape

Common body shapes for modern acoustic guitars, from smallest to largest:

Range – The smallest common body shape, sometimes called a mini jumbo, is three-quarters the size of a jumbo-shaped guitar. A range shape typically has a rounded back to improve projection for the smaller body. [13] The smaller body and scale length make the range guitar an option for players who struggle with larger body guitars.

ParlorParlor guitars have small compact bodies and have been described as “punchy” sounding with a delicate tone. [14] It normally has 12 open frets. The smaller body makes the parlor a more comfortable option for players who find large body guitars uncomfortable.

Grand Concert – This mid-sized body shape is not as deep as other full-size guitars, but has a full waist. Because of the smaller body, grand concert guitars have a more controlled overtone [15] and are often used for its sound projection when recording.

Auditorium – Similar in dimensions to the dreadnought body shape, [16] but with a much more pronounced waist. The shifting of the waist provides different tones to stand out. The auditorium body shape is a newer body when compared to the other shapes such as dreadnought.

Dreadnought – This is the classic guitar body shape. The style was designed by Martin Guitars [17] to produce a deeper sound than "classic"-style guitars, with very resonant bass. Used for over 100 years, it is still the most popular body style for acoustic guitars.[ citation needed ] The body is large and the waist of the guitar is not as pronounced as the auditorium and grand concert bodies. This allows mid-range frequencies to stand out, helping the guitar cut through an ensemble of instruments.[ citation needed ]

Jumbo – The largest standard guitar body shape found on acoustic guitars. The large body provides more punch and volume, while accenting the "boomy" low end of the guitar.[ citation needed ] Jumbo is bigger than a Grand Auditorium but similarly proportioned, and is generally designed to provide a deep tone similar to a dreadnought's. It was designed by Gibson to compete with the dreadnought, [17] but with maximum resonant space for greater volume and sustain. These come at the expense of being oversized, with a very deep sounding box, and thus somewhat more difficult to play.[ citation needed ] The foremost example of the style is the Gibson J-200, but like the dreadnought, most guitar manufacturers have at least one jumbo model.

## Related Research Articles

The steel-string acoustic guitar is a modern form of guitar that descends from the nylon-strung classical guitar, but is strung with steel strings for a brighter, louder sound. Like the classical guitar, it is often referred to simply as an acoustic guitar.

The classical guitar is a member of the guitar family used in classical music. An acoustic wooden string instrument with strings made of gut or nylon, it is a precursor of the acoustic and electric guitars which use metal strings. Classical guitars are derived from the Spanish vihuela and gittern in the fifteenth and sixteenth century, which later evolved into the seventeenth and eighteenth century Baroque guitar and later the modern classical guitar in the mid nineteenth century.

An electric guitar is a guitar that uses one or more pickups to convert the vibration of its strings into electrical signals. The vibration occurs when a guitar player strums, plucks, fingerpicks, slaps or taps the strings. The pickup generally uses electromagnetic induction to create this signal, which being relatively weak is fed into a guitar amplifier before being sent to the speaker(s), which converts it into audible sound.

The guitar is a fretted musical instrument that usually has six strings. It is typically played with both hands by strumming or plucking the strings with either a guitar pick or the fingers/fingernails of one hand, while simultaneously fretting with the fingers of the other hand. The sound of the vibrating strings is projected either acoustically, by means of the hollow chamber of the guitar, or through an electrical amplifier and a speaker.

String instruments, stringed instruments, or chordophones are musical instruments that produce sound from vibrating strings when the performer plays or sounds the strings in some manner.

A chordophone is a musical instrument that makes sound by way of a vibrating string or strings stretched between two points. It is one of the four main divisions of instruments in the original Hornbostel-Sachs scheme of musical instrument classification.

An electric piano is an electric musical instrument which produces sounds when a performer presses the keys of the piano-style musical keyboard. Pressing keys causes mechanical hammers to strike metal strings, metal reeds or wire tines, leading to vibrations which are converted into electrical signals by magnetic pickups, which are then connected to an instrument amplifier and loudspeaker to make a sound loud enough for the performer and audience to hear. Unlike a synthesizer, the electric piano is not an electronic instrument. Instead, it is an electro-mechanical instrument. Some early electric pianos used lengths of wire to produce the tone, like a traditional piano. Smaller electric pianos used short slivers of steel to produce the tone. The earliest electric pianos were invented in the late 1920s; the 1929 Neo-Bechstein electric grand piano was among the first. Probably the earliest stringless model was Lloyd Loar's Vivi-Tone Clavier. A few other noteworthy producers of electric pianos include Baldwin Piano and Organ Company and the Wurlitzer Company.

The acoustic bass guitar is a bass instrument with a hollow wooden body similar to, though usually larger than a steel-string acoustic guitar. Like the traditional electric bass guitar and the double bass, the acoustic bass guitar commonly has four strings, which are normally tuned E-A-D-G, an octave below the lowest four strings of the 6-string guitar, which is the same tuning pitch as an electric bass guitar.

A sound board, or soundboard, is the surface of a string instrument that the strings vibrate against, usually via some sort of bridge. Pianos, guitars, banjos, and many other stringed instruments incorporate soundboards. The resonant properties of the sound board and the interior of the instrument greatly increase the loudness of the vibrating strings. "The soundboard is probably the most important element of a guitar in terms of its influence on the quality of the instrument's tone [timbre]."

When the [guitar] top vibrates, it generates sound waves, much like a loudspeaker. As the soundboard moves forward, the air that is in front of it is compressed and it moves away from the guitar. As the soundboard moves back, the pressure on the air in front of the guitar is reduced. This is called a "rarefaction," and air rushes in to fill the rarefied region. Through this process, an alternating series of compression and rarefaction pulses travel away from the soundboard, creating sound waves.

The electric cello is a type of cello that relies on electronic amplification to produce sound. An acoustic cello can be fitted with a bridge or body mounted contact pickup providing an electric signal, or a built-in pickup can be installed. A few pickups work by other principles like magnetic coil guitar type needing steel strings to work, or by an unusual pickup system employing the string itself as a linear pickup element, thus avoiding any modification of tone-producing parts on an acoustic cello.

An "archtop guitar" is a hollow steel-stringed acoustic or semiacoustic guitar with a full body and a distinctive arched top, whose sound is particularly popular with jazz, blues, and rockabilly players.

A pickup is a transducer that captures or senses mechanical vibrations produced by musical instruments, particularly stringed instruments such as the electric guitar, and converts these to an electrical signal that is amplified using an instrument amplifier to produce musical sounds through a loudspeaker in a speaker enclosure. The signal from a pickup can also be recorded directly.

The yueqin or yue qin, formerly romanized as yüeh-ch‘in and also known as the moon guitar, moon zither, gekkin, wolgeum, or la-ch‘in, is a traditional Chinese string instrument. It is a lute with a round, hollow wooden body which gives it the nickname moon guitar. It has a short fretted neck and four strings tuned in courses of two, generally tuned to the interval of a perfect fifth. Occasionally, the body of the yueqin may be octagonal in shape. It is an important instrument in the Peking opera orchestra, often taking the role of main melodic instrument in lieu of the bowed string section. The frets on all Chinese lutes are high so that the fingers never touch the actual body—distinctively different from western fretted instruments. This allows for a greater control over timbre and intonation than their western counterparts, but makes chordal playing more difficult.

A sound hole is an opening in the body of a stringed musical instrument, usually the upper sound board. Sound holes have different shapes:

The following outline is provided as an overview of and topical guide to guitars:

Plucked string instruments are a subcategory of string instruments that are played by plucking the strings. Plucking is a way of pulling and releasing the string in such a way as to give it an impulse that causes the string to vibrate. Plucking can be done with either a finger or a plectrum.

A bridge is a device that supports the strings on a stringed musical instrument and transmits the vibration of those strings to another structural component of the instrument—typically a soundboard, such as the top of a guitar or violin—which transfers the sound to the surrounding air. Depending on the instrument, the bridge may be made of carved wood, metal or other materials. The bridge supports the strings and holds them over the body of the instrument under tension.

Guitar bracing refers to the system of wooden struts which internally support and reinforce the soundboard and back of acoustic guitars.

Collings Guitars is an Austin, Texas based stringed instrument manufacturer. The company was founded in 1973 by Bill Collings who in 2008 was called "one of the most recognized and respected names amongst aficionados of modern acoustic instruments". Their acoustic guitars have been highly regarded for decades. In addition to acoustic guitars they also make electric guitars, archtop guitars, mandolins, and ukuleles.

Lichty Guitars is an American company based in Tryon, North Carolina, that has been making custom acoustic guitars and ukuleles since 2009. It was founded by musician Jay Lichty, who honed his craft with luthier Wayne Henderson.

## References

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4. Tyler, James (2002). The Guitar and its Music. United Kingdom: Oxford University Press. pp. 229–231. ISBN   978 0 19 921477 8.
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9. Carter (1996 , p. 127)
10. Denyer (1992 , pp. 44–45)
11. Denyer (1992 , p. 48)
12. Carter (1996 , pp. 48–52)
13. "Teton Range Guitars Demo - Home on the Range - Teton® Guitars". November 20, 2015. Retrieved August 29, 2016.
14. "Parlor Pickin': The 2015 Guide to Buying a Parlor Guitar". Acoustic Guitar. Retrieved February 16, 2016.
15. "Grand Concert". Taylor Guitars. Retrieved February 16, 2016.
16. "Auditorium Body Shape Overview". breedlovemusic.com. Retrieved February 16, 2016.
17. "Acoustic Guitar Buying Guide". www.sweetwater.com. Retrieved August 11, 2015.