See also: Acoustic Guitar (magazine)

An acoustic guitar is a guitar that uses only acoustic methods to project the sound produced by its strings. The guitar is a Musical instrument with ancient roots that is used in a wide variety of musical styles It is a retronym, coined after the advent of electric guitars, which depend on electronic amplification to make their sound audible. A retronym is a type of Neologism coined for an old object or concept whose original name has come to be used for something else is no longer unique or is otherwise inappropriate An electric guitar is a type of Guitar that uses pickups to convert the vibration of its steel-cored strings into an electrical current which is made louder

Contents 1 Sound production 1.1 Amplification 2 Construction 3 Types 4 References 5 See also

Sound production

In all types of guitars the sound is produced by the vibration of the strings. Vibration refers to mechanical Oscillations about an equilibrium point. However, because the strings can only displace a small amount of air, the volume of the sound needs to be increased in order to be heard. In an acoustic guitar, this is accomplished by using a soundboard and a resonant cavity, the sound box. The sounding board or soundboard is the part of a String instrument that transmits the vibrations of the strings to the air greatly increasing the Loudness A resonator is a device or system that exhibits Resonance or resonant behavior that is it naturally oscillates at some frequencies, called its resonance A sound box or sounding box, (sometimes written soundbox) is an open chamber in the body of a Musical instrument which alters the instrument's tone quality The body of the guitar is hollow. The vibrating strings drive the soundboard through the bridge, making it vibrate. The soundboard has a larger surface area and thus displaces a larger volume of air, producing a much louder sound than the strings alone.

As the soundboard vibrates, sound waves are produced from both the front and back faces. The sound box provides both a support for the sound board and a resonant cavity and reflector for the sound waves produced on the back face of the soundboard. The air in this cavity resonates with the vibrational modes of the string (see Helmholtz resonance), increasing the volume of the sound again. Helmholtz resonance is the phenomenon of air Resonance in a cavity The back of the guitar will also vibrate to a lesser extent, driven by the air in the cavity. Some sound is ultimately projected through the sound hole^[1] (some variants of the acoustic guitar omit this hole, or have f holes, like a violin family instrument). The Violin family of Musical instruments was developed in Italy in the Sixteenth century. This sound mixes with the sound produced by the front face of the soundboard. The resultant sound is a complex mixture of harmonics that give the guitar its distinctive sound. In Acoustics and Telecommunication, the harmonic of a Wave is a component Frequency of the signal that is an Integer

No amplification actually occurs in this process, in the sense that no energy is externally added to increase the loudness of the sound (as would be the case with an electronic amplifier). Loudness is the quality of a Sound that is the primary psychological correlate of physical strength (amplitude All the energy is provided by the plucking of the string. The function of the entire acoustic system is to maximize intensity of sound, but since total energy remains constant, this comes at the expense of decay time. An unamplified guitar (one with no soundboard at all) would have a low volume, but the strings would vibrate much longer, like a tuning fork. This is because a damped harmonic oscillator decays exponentially, with a mean life inversely proportional to the damping. When the strings are driving the larger soundboard and sound box, the damping is much higher.

Amplification

An acoustic guitar can be amplified by using various types of pickups or microphones. 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. Magnetic pickups are generally mounted in the sound hole of the acoustic guitar and are very similar to those found in electric guitars.

Construction

Various shapes determine the way the soundboard vibrates. The thinner and lighter the soundboard (less mass), the louder the sound. However, there are practical limitations to how thin the soundboard can be made without breaking. Braces are used inside the guitar to provide strength and resilience. Tensile strength \sigma_{UTS} or S_U is the Stress at which a material breaks or permanently deforms Resilience is the property of a material to absorb energy when it is deformed elastically and then upon unloading to have this energy recovered The mass and position of these braces have consequences for the range of frequencies reproduced. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object Frequency is a measure of the number of occurrences of a repeating event per unit Time. During the wave cycle, different regions of the soundboard may be moving in different directions, depending on the sound frequency. Different configurations of bracing and different shapes of soundboard produce different vibration patterns, giving subtle variations in the range of sounds produced. ^[2]

The materials and shape of the guitar produce a complex series of damping, resonating, and phase cancelling or reinforcing effects. Damping is any effect either deliberately engendered or inherent to a system that tends to reduce the amplitude of Oscillations of an oscillatory system Acoustic resonance is the tendency of an acoustic system to absorb more energy when the Frequency of its oscillations matches the system's natural frequency of vibration The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0 The range of factors determine the overall acoustic qualities or timbre of the instrument. Musical acoustics or music acoustics is the branch of Acoustics concerned with researching and describing the Physics of Music — how sounds In Music, timbre (ˈtæm-bər' like timber, or, from Fr timbre tɛ̃bʁ is the quality of a Musical note or sound that distinguishes different Artisan luthiers tap potential pieces of wood to determine their acoustic resonance, but this is usually not done for mass-produced instruments. Acoustic resonance is the tendency of an acoustic system to absorb more energy when the Frequency of its oscillations matches the system's natural frequency of vibration Different timber species have different tones and careful selection of timber is required when designing and making an instrument. Lumber or timber is Wood in any of its stages from felling through readiness for use as structural Material for Construction, or Acoustic resonance is the tendency of an acoustic system to absorb more energy when the Frequency of its oscillations matches the system's natural frequency of vibration Guitars have been made with steel soundboards and resonators, and some experiments have been conducted with novel materials including aluminium and plastics^[3]. A resonator is a device or system that exhibits Resonance or resonant behavior that is it naturally oscillates at some frequencies, called its resonance Even the hardness or viscoelasticity of the glues and varnishes can have a dramatic effect on the sound, damping or resonating some or all frequencies. Viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Damping is any effect either deliberately engendered or inherent to a system that tends to reduce the amplitude of Oscillations of an oscillatory system Acoustic resonance is the tendency of an acoustic system to absorb more energy when the Frequency of its oscillations matches the system's natural frequency of vibration Frequency is a measure of the number of occurrences of a repeating event per unit Time. Quality instruments are made with hard glues and lacquers which have less damping on the transmission of vibrations around the structure of the instrument. Hardness refers to various properties of Matter in the Solid phase that give it high resistance to various kinds of shape change when Force Glue or adhesive is a compound that adheres or bonds two items together In a general sense lacquer is a clear or coloured Varnish, that dries by solvent evaporation and often a curing process as well that produces a hard durable finish in any Damping is any effect either deliberately engendered or inherent to a system that tends to reduce the amplitude of Oscillations of an oscillatory system Most people prefer the sound of wooden instruments, although the steel resonator guitar has found favor in some genres, like blues. A resonator guitar or resophonic guitar is an acoustic guitar whose sound is produced by one or more metal cones ( Resonators ' instead of the The Blues is a vocal and instrumental form of Music based on the use of the Blue notes It emerged as an accessible form of self-expression Sitka spruce is traditionally the favored material for the soundboard because of its high strength-to-weight ratio and stiffness. The Sitka Spruce ( Picea sitchensis) is a large Coniferous Evergreen Tree growing to 50-70 m tall exceptionally to 100 m tall and In recent years King William pine has been found to produce very good results. Athrotaxis selaginoides is a species of Athrotaxis, endemic to Tasmania in Australia, where it grows at 400–1120

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 (nylon-stringed), steel-string acoustic guitar and lap steel guitar. A steel-string acoustic guitar, is a modern form of Guitar descended from the Classical guitar, but strung with steel strings for a brighter louder sound The lap steel guitar is a type of Steel guitar, from which other types developed A more complete list is given below, refer to the individual articles for more specific detail.

• Nylon/gut stringed guitars:
  • Renaissance guitar
  • Baroque guitar
  • Romantic guitar
  • Classical guitar, the modern version of the original guitar, with nylon strings
  • 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
  • Battente guitar
  • Lap steel guitar
  • Lyre guitar
• Acoustic bass guitar
• Russian guitar
• Novelty instruments:
  • Harp guitar
  • Banjo guitar
  • Guitar lute

References

See also

• Types of guitar

This article is about baroque guitars For the modern 10-string guitar see Ten-string guitar. The Romantic guitar is the guitar of the Romantic period of Classical music (c A flamenco guitar is a type of Classical guitar, built for the purpose of playing Flamenco music A steel-string acoustic guitar, is a modern form of Guitar descended from the Classical guitar, but strung with steel strings for a brighter louder sound A resonator guitar or resophonic guitar is an acoustic guitar whose sound is produced by one or more metal cones ( Resonators ' instead of the Dobro is a Trade name now owned by Gibson Guitar Corporation and used for a particular design of Resonator guitar. An archtop guitar is a steel-stringed acoustic or semi-acoustic Guitar with a full body and a distinctive arched top whose sound is particularly The Guitar battente ( Chitarra battente) is an important string instrument in Italian popular music. The lap steel guitar is a type of Steel guitar, from which other types developed The acoustic bass guitar (also called ABG or acoustic bass) is a bass instrument with a hollow wooden body similar to though usually somewhat larger than a steel-string The Russian guitar is a seven-string acoustic Guitar that arrived in Russia toward the end of the 18th century and the beginning of the 19th century most probably The harp guitar (or "harp-guitar" is a stringed instrument with a history of well over two centuries Guitjo is a Plucked string instrument in the guitar or banjo family Lute can refer generally to any plucked string instrument with a neck (either Fretted or unfretted and a deep round back or more specifically to an instrument from The guitar is a Musical instrument with ancient roots that is used in a wide variety of musical styles

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