by David Pitts

Created on: January 10, 2009

The term, acoustic, means that the sound is amplified by a natural means. Both acoustic and electric guitar generate the musical sound by causing a stretched string to vibrate at a particular frequency. The frequency of vibration is determined by the length and the size or density of the string. The same is true for electric guitars. The difference is how the sound is amplified so it can be readily heard.

Acoustic guitars use the shape and tonal characteristics of the guitar body itself to embellish and increase the tone. The sound of the vibrating strings travels through the sound hole or holes into the main part of the guitar. The acoustic shape and characteristics of the guitar's wood and design cause the guitar body itself and the air inside to vibrate at the frequency of the plucked string. The vibrating air and guitar body cause the surrounding air to vibrate and travel to the ears. The art and science of guitar shapes, designs, and woods have evolved through the years. The best woods and designs are the ones that produce the loudest, truest, and sweetest tones. Unfortunately, these are also usually the most expensive.

Electric guitars use electronic pickups to capture the vibrations. For solid body guitars, there is no internal sound chamber. The pickups are typically mounted under the strings. There can be several sets of pickups that can be switched or selected in combination to vary the sound. The vibrations are converted to electrical signals that are transmitted through the cable to an amplifier. The amplifier converts the electrical signals back into sound by vibrating a speaker cone using a magnetic technique. The vibrating speaker cone causes the air around it to vibrate and travel to the ears of the listener. Electronics in the pickups, the guitar, and the amplifier allow the signal to be changed to create a variety of interesting sounds. These enhancements such as distortion are based on the original plucked string, but can be quite different to the listener.

Another guitar variation is the acoustic electric. These guitars have the inherent acoustic characteristics to be played without electrical amplification. The intent is to preserve the original "sweet" acoustic sound as much as possible, but to provide electrical amplification and tone enhancement suitable for performance in larger venues. Sound variations are applied, however, at the discretion of the player and the equipment being used.

Typically, the "action" of the guitar is closer for an electric guitar, especially a solid body electric. The strings are closer to the frets and easier to push down, allowing the player to execute much faster passages. Achieving close action on the neck of an acoustic guitar is more difficult. Good action costs money, so the really close action, great sounding acoustic guitars are expensive.

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