How a Guitar Works Essay Example for Free

How a Guitar Works Essay A guitar can be defined as a musical instrument having â€Å"a long, fretted neck, flat wooden soundboard, ribs, and a flat back, most often with incurved sides† (Kasha, 1968) and believed to exist over 4000 years ago. The instrument was believed to be derived from the Greek instrument kithara, â€Å"a square-framed lap harp or lyre† (Guy, 2001). Today the guitar comes in many different forms but still follows the same dynamics to create beautiful melody. Music classifies a guitar as a chordophone or a string instrument. Physics describe a chordophone is any â€Å"instrument whose standing wave constraint is that at each end of the medium there must be a node† (Lapp, p. 61). A guitar has four essential components namely its hollow body, its neck, the head and its six strings. The body is the enclosed part of the guitar composed of the soundboard, a flat wooden piece that comprises the front of the body, supported by the wooden ribs and braces connected to the back board of the guitar to form the body cavity where air vibrates. The soundboard is etched with the sound hole, the hole where which the sound from the vibration travels out into the air. The bridge, which is mounted on the lower part of the soundboard, anchors each of the one ends of the six strings of the guitar. A thin piece is attached to the bridge, which is called the saddle, on which the strings rest. The guitar neck is made up of the fingerboard, the face of the neck where the fingers of the player are placed while pressing on a string. Frets, pieces the separate the fingerboard at definite intervals, are also part of the neck of the guitar. The end of the neck is made up of the nut, on which the other end of the strings rest, functioning similarly as the saddle. The head of the neck are where the ends of the string are affixed. The strings are tied onto a string post which can be freely rotated through worm gears. The tuning knobs provide for the control of the movement of the worm gears. Turning these knobs, enables the player to increase or decrease tension in the strings. The strings are the one who provides the tone that the guitar plays. Guitars have strings with different thickness for steel string guitars or densities for nylon string guitars, having its thickness or density increase gradually from top to bottom. The vibration of the strings determines the sound that the guitar plays. The vibrating strings alone are hardly audible. In order for the sound produced to be recognizable, the structure of the guitar is made as such in order to transfer the string vibrations to the plate of the soundboard through the bridge and saddle. The body then vibrates in all directions; however the ribs inside the body cavity keep the plate flat, despite these disturbances. Amplification, in the strictest definition of the word, is never the function of the guitar body. The small volume of sound produced due to string vibration is mostly due to the inefficient conversion of the energy from the plucking of the string into sound energy. The guitar body provides an efficient medium for this energy conversion due to its large surface area. The simple schematic below, cited as Fig. 1, demonstrates the transfer of energy as a guitar string is plucked. Figure 2. Energy Transfer in the Guitar Physics in Guitars Sound is any fluctuation is pressure resulting from the displacement of matter. However, what men recognize as being heard are tones, which are sounds that are repeated at a specific frequency. Humans can only recognize tones with frequencies between 20Hz and 20kHz. Musical notes, however, are collection of tones with specific frequencies that were found pleasing to one’s senses. The basic notes of the musical scale and their specific frequencies are as follows: 264Hz is middle C or middle do; 297Hz is D or re; 330Hz is E or mi; 352Hz is F or fa; 396Hz is G or so; 440Hz is A or la; 495Hz is B or ti; and 528Hz is the higher C or higher do. The masterful combination of these basic set of frequencies by musical composers enabled the conception of melodic harmony and symphony. The vibration of the strings of the guitar can be characterized as standing waves. The standing wave condition needs that the ends be terminated by a fixed node. The frequency of the vibration is determined by the length of the string and the tension experienced by the string. Therefore, in order to produce the different musical notes, the different frequencies of vibration should be achieved by the strings. The first mode of vibration or the fundamental harmonic of the string can be illustrated by the Fig. 2, where L is the length of the string and ? represents the wavelength, the length of one cycle of vibration, an upward movement and its corresponding downward movement along the string. Figure 2. Fundamental Harmonic of String (Lapp, p. 62) ? can be found to be twice of the string length, L. Since frequency is the ratio of the speed of vibration and the wavelength and the tension of the string is the product of the mass density or mass per unit length of the string and the speed of vibration, an expression of the frequency of vibration, expressed as f, in terms of the string tension, expressed as T, mass density of the string, expressed as ? , and L can be derived, thus the expression: These factors determine the frequency of the vibration, thus the tone that is played. An increase in ? and L decreases f, which results in a lower pitch. On the other hand, an increase in T, increases f, resulting in a higher pitch. The guitar provides control for all these factors. The difference in the density of the strings from top to bottom provides control for ?. The tuning knobs manage T while L is controlled by the player by pressing on the string against the fret. However, as the guitar string is struck, it does not vibrate solely on its fundamental frequency. Instead overtones are formed, which are harmonics with frequencies that are integer multiples of the fundamental frequency, which can be demonstrated by Fig. 3. These overtones provide the richness of sound, which seem to reverberate in one’s ears, instead of a flat sound of a tone with only a single harmonic. Figure 3. (from top to bottom) 1st, 2nd, and 3rd overtones (Hokin, 2001) â€Å"The guitar can be considered to be a system of coupled vibrators† (Fletcher Rossing, 1998, p. 240). Along with the vibration of the string as it is plucked, all other parts of the guitar vibrates, and with it energy is transferred through them as demonstrated in Fig. 1. A significant part of the production of tones of a guitar is the vibration of the body along with air inside its cavity. The movements and modes of vibration of the guitar body and the air inside it, in response to the string being plucked, are referred to as internal resonances, which provides for the increase in volume of the tone produced similar to hitting a snare. The frequency of thses internal resonances of the guitar body are determined by the volume of air that the body encloses and the size of the sound hole, one of which that has lowest frequency is termed as Helmholtz resonance. These modes of the vibration can be observed through the use of lasers in holographic interferograms, as exemplified by Fig. 4, wherein the vibrations are manifested as ripples in the guitar body. Figure 4. Guitar Body Resonances (Fletcher Rossing, 1998, p. 246) However, these resonances can affect the quality of the tone produced when its frequency is close to harmonics that the plucked string produces. Certain harmonics are attenuated further than usual resulting in higher or lower pitches. The appropriate placement of the ribs and braces inside the guitar body, aside from supporting the soundboard, keep these resonances at a minimum. The ribs and braces of the guitar are illustrated below. Figure 5. Bracings of a Guitar (Billington, 1999) The masterful combination of the components of a guitar through its development has enabled it to be a source of beautiful melody throughout generations. The guitar is concrete evidence how man can create harmony from chaos. References Flectcher, N. H. Rossing, T. D. (1998). The Physics of Musical Instruments. 2nd ed. New York. Springer Science+Business Media, Inc. Billington, I. (1999). The Physics of the Acoustic Guitar. Retrieved from http://ffden-2. phys. uaf. edu/211. web. stuff/billington/main. htm. University of New South Wales. Guitar Acoustics. Retrieved from http://www. phys. unsw. edu. au/music/guitar/. Hokin, S. (2002). The Physics of Everyday Stuff. Retrieved from http://www. bsharp. org/ physics/ stuff/guitar. html. Lapp, D. R. The Physics of Music and Musical Instruments. Retrieved from http://www. tufts. edu/as/wright_center/workshops/workshop_archives/physics_2003_wkshp/ book/pom_book_acrobat_7. pdf. Brain, M. How Acoustic Guitars Work. Retrieved from http://entertainment. howstuffworks. com/guitar. htm. Guy, P. (2001). A Brief History of the Guitar. Retrieved from http://www. guyguitars. com/eng/ handbook/BriefHistory. html Parkkali, R. (2006). A Well Compensated Guitar. Retrieved from http://www. newmillguitar. com/ millen2. htm