Air and Amplification


Previously, we have learned that strings vibrate, producing sound waves, which is what gives the guitar its purpose. However, if it weren’t for the body of a guitar, the vibration of the strings would barely be audible. The body of the guitar amplifies the sound of the strings, making it possible for it to reach the ears of the listeners.


Acoustic Amplification

 

When a player plucks the guitar strings, the strings vibrate, which transfers the mechanical energy down the strings to the guitar's bridge, which is attached to the guitars body. This transfer of energy causes the top plate, also called the soundboard, to vibrate as well. The soundboard is most often made of a thin piece of wood, which is designed to easily vibrate. The vibration of the soundboard then causes the air inside the guitar cavity to vibrate. When the molecules of air closest to the soundboard start vibrating, they bump into the other particles around them, and soon there is a symphony of dancing air molecules inside the guitar. This is where the sound hold finds its purpose. The sound hole is where all the vibrating air escapes from the guitar’s body and is projected out, reaching the ears of the listeners.


 
Acoustic Diagram

http://www,guitarfriendly.net/the-parts-of-the-guitar/


Electric Amplification

 

Electric guitar work a bit differently than their acoustic cousins. The main difference is that electric guitars have a solid wood body, and instead of using a soundboard for amplification, they rely on electronic pickups. The pickups do their name justice, and “pick up” the sound vibrations from the plucked string, and convert these vibrations into electronic signals that are then read by an amplifier. The pickups are essentially electromagnets, consisting of a bar magnet wrapped in fine conducting wire. The vibrating steel strings above the pickup causes a change in magnetic flux in the system. According to Lenz’s Law, "there is an induced current in a closed, conducting loop if and only if the magnetic flux through the loop is changing" (Knight 972). This change in the flux through the closed loop generates a voltage, or emf, by Faraday’s Law. This produced voltage then sends the induced current to the amplifier.


 
Electric Diagram

http://www,guitarfriendly.net/the-parts-of-the-guitar/



Once the induced current has traveled to the amplifier, it now can be manipulated or distorted in any way that the musician desires using a series of different resistors, transistors, and other elements of electrical circuitry. This current then vibrates the diaphragm of the speaker inside the amp to produce a frequency that is identical to that of the original plucked string.

Guitar Amplifier

http://www.georgesmusic.com/fender-mustang-i-v2-20-watt-1x8-inch-combo-electric-guitar-amplifier.html


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