Important Characteristics of an Acoustic Guitar
The acoustics of a guitar are no less important than the overall design of the guitar. A guitar's acoustics depend a lot on how the guitar is made. In fact the three main contributions to the acoustics of a guitar are the coupling, the materials used and plate bracing.
In order to get a good sound from a guitar the vibrations should produce the right sound. You start first by applying some force to the string, usually by plucking or strumming. This causes the strings and bridge to vibrate, which stimulates the soundboard causing the airwaves and vibrations to go into the guitar; this is when coupling occurs. As the airwaves travel around the sound box they continue to vibrate and this produces the sound. If you want to produce a good sound the individual elements need to work harmoniously together. When the guitar is properly tuned then the sound waves will create a harmonious sound. This is when the guitar is coupled together and working well.
The sound box or body of the guitar effects the way the sound waves travel. The box needs to take high pitch and high pressure vibrations from the bridge into low pressure vibrations in the surrounding air. The higher sounds on the guitar are created by the strings and bridge while the lower sounds are created by the design of the sound box. This is the most important influence on how the sound is created. How the strings are actually played and how the vibrations flow are only secondary in their influence on the sound.
How the guitar parts interact with each other depends on the materials that are used, where the parts are placed, the resonance and how the mathematics of sound and frequency affect the overall design. To understand it better you can compare it to the different instruments that are played in an orchestra. Each piece affects how the whole sound is made therefore every piece needs to work in harmony to create a good sound. The sounds cannot be too coupled otherwise the overall sound will be rather harsh and unappealing.
It is easy to see how the sound a guitar makes is mainly dependent on the coupling, the materials used and the plate bracing. The coupling affects whether the sounds will be high pitched or low pitched. The plate bracing also affects how the high pitched sounds are created because it is how the strings interact with the plate bracing that affects the high pitched sounds. The construction of the guitar also affects how the sound waves travel so the construction of this is very important in the overall sound.
When you are looking at a guitar pay attention to all the details including the overall design, the materials that are used, how all the pieces are connected, where the bridge is placed and what the bridge is constructed of. It is the correct combination of all these details that produces the best sound in a guitar.