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An acoustic guitar is a musical instrument in the string family. When a string is plucked, its vibration is transmitted from the bridge, resonating throughout the top of the guitar. It is also transmitted to the side and back of the instrument, resonating through the air in the body, and producing sound from the sound hole. The original, general term for this stringed instrument is guitar, and the retronym 'acoustic guitar' distinguishes it from an electric guitar, which relies on electronic amplification. 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.
Guitar strings may be plucked individually with a
The guitar likely originated in Spain in the early 16th century, deriving from the guitarra latina.
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. 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 related to the guitar and its structure were broadly known as vihuelas within Spanish musical culture. Vihuelas were string instruments that were commonly seen in the 16th century during the
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 book Arte de tocar la Guitarra Española por Música (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.
Finally, circa 1850, the form and structure of the modern guitar are credited to Spanish guitar maker
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. 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
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
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 United States firm C.F. Martin: steel strings and the increasing of the guitar top area; the popularity of Martin's larger "dreadnought" body size among 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 reinforced the neck with a steel truss rod, which became standard in later steel-string guitars.
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. 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. Another method for reducing feedback is to fit a rubber or plastic disc into the sound hole.
The most common types of pickups used for acoustic guitar amplification are piezo and magnetic pickups.
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.
Historical and modern acoustic guitars are extremely varied in their design and construction. Some of the most important varieties are the classical guitar (Spanish Guitar/Nylon-stringed), steel-string acoustic guitar and lap steel guitar.
- Nylon/gut stringed guitars:
- Baroque guitar
- Romantic guitar
- Classical guitar, the modern version of the original guitar, including additional strings models
- Flamenco guitar
- Steel stringed guitars:
- Steel-string acoustic guitar, also known as western, folk or country guitar
- Twelve string guitar
- Resonator guitar (such as the Dobro)
- Archtop guitar
- Selmer/Maccaferri (Manouche) guitar
- Battente guitar
- Lap steel guitar
- Lap slide guitar
- Parlor guitar
- Other variants:
- Harp guitar
- Pikasso guitar(a variant of harp guitar)
- Contraguitar (Viennese variant of harp guitar)
- Acoustic bass guitar
- Banjo guitar
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. The smaller body and scale length make the range guitar an option for players who struggle with larger body guitars.
Parlor – Parlor guitars have small compact bodies and have been described as “punchy” sounding with a delicate tone. 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 and are often used for their sound projection when recording.
Auditorium – Similar in dimensions to the dreadnought body shape, but with a much more pronounced waist. This general body shape is also sometimes referred to as an "Orchestra" style guitar depending on the manufacturer. 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.
Jumbo – The largest standard guitar body shape found on acoustic guitars. Jumbo is bigger than an 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, but with maximum resonant space for greater volume and sustain. The foremost example of the style is the Gibson J-200, but like the dreadnought, most guitar manufacturers have at least one jumbo model.
Lute (17th century)
Romantic guitar (c. 1830)
Steel guitar (c. 1920)
12-String acoustic guitar
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- Media related to Acoustic guitarsat Wikimedia Commons