Perhaps somebody will comment about such an article is difficult to understand. But I believe you must get a complete knowledge for the guitar instrument after you reading well.
1. The sound is a mechanical wave
The sound is a mechanical wave, which is waving along with the subject (sound source) waving and waving the air, then forming as a sound wave.
The guitar sound principle as below diagram, which waving transfer to the guitar top trough the saddle and the bridge, and the waving guitar top then pressing the air of guitar body, which waving the air and created the sound wave.
The basic sound wave named simple harmonic oscillation (which mentioned as below) created the sinusoidal wave. Traditional musical instrument usually depends on the simple harmonic oscillation to make the sound, such as the string, drum and so on, which sound is the sinusoidal wave.
According to the law of conservation of energy, from playing too loudly sound, which are energy conservation of your finger, the guitar itself doesn’t add additional power.
2. The waving of the guitar strings is a simple harmonic oscillation
The simple harmonic oscillation is an easiest simple mechanical waving when the subject making the simple harmonic oscillation, its power is equal to the offset and the power is the point to the balance location.
The sound is louder when you are playing closer to the sound hole also the sound is louder when you are playing with more power and the range of the waving is wider.
3. The sound while playing the strings is equal to many overtones added fundamental tone
The pure tone is called by some fixed frequency and waving by simple harmonic, but in fact, there is no the absolutely pure tone in the world at all, such as the tuning fork which is closer to the pure tone sound. It is not the pure tone at all when you just play only one string of the guitar, actually, which sound is combined by the fundamental tone and several different frequent waving.
We named the standard sinusoidal wave as a basic, called basic wave. The harmonic wave is a wave of which frequency is higher than the basic wave. When you play the guitar for only one string or pressing the key on the piano which basic wave will create many harmonic waves, usually we called it as an overtone in the music industry.
For example, the pure sound wave frequent is f while you are playing some strings of the guitar, and see this pure sound like a basic wave, and the harmonic waves can be 2f, 3f, 4f......， all these harmonic waves called the second harmonic waves, the third harmonic waves, the fourth harmonic waves. You can refer to diagram 2
The actual sound wave superimposed of the sound can see the below diagram, the top one is the basic wave, and the following ones are the second harmonic wave, the third harmonic wave and so on. In fact, all of the traditional musical instrument sounds are a compounding tone, which is constituted by the biggest range basic wave and some smaller range harmonic wave. So that we can define for the single tone: the single tone means a sound wave( compounding by harmonic waves) created by playing one musical instrument and playing single sound, which basic wave frequent called as pitch. The different single tones of different musical instrument which compounded harmonic wave and ranges are different, therefore, that is why so many different sounds for thousands of musical instrument.
5、The strong guitar top
The makers of guitars are well known the top is the most important parts of the guitar. In fact, some well original sound back and side are plastic, however, choosing the wood material as the top would be better.
Do you know how difficult it is for the good original sound? Each string undertakes more than thousand-kilogram pulling, but the guitar normally with 6 strings, you can see that then how difficult for the guitar to undertake the capability which almost equal to one package of concrete, at the same time, the thinner of the wood the louder of the guitar. We usually selected the cedar or spruce as the top because of these materials with strong tensile resistance.