how do guitar strings create noise and why are harmonics apperently only achievable on certain points?

Question

*at certain points along the string

Answer 1

A guitar string supports a note because we tune them that way.

We increase the tension on the string until we have just enough space to fit some multiple of half-wavelengths. This frequency is called the fundamental. You can't make a lower note with this string tuned this way, but you can make higher notes. That's what you're doing when you press it against the fretboard.

At certian points along the string, you'd see that the string vibrates a great deal when struck, and there are points where the string would not move at all. These points that are sitting still are called nodes. And the points in between, anti-nodes.

The rule is that you must have some multiple of half-wavelengths along the string at all times, otherwise it will not resonate with a standing wave (and would die out quickly). A harmonic is a doubling of the frequency, by damping the string at the center node. The string is half as long, and your note is one octave up.

Forgive me if I get the music wrong, I come from the science side of things.

Answer 2

First, guitar strings don't create noise, they create music, and
the harmonics are what makes their sound music. Harmonics are vibrations of equal-length divisions of a string. The first harmonic divides the string into two segments, which each vibrate at twice the frequency of the whole string (known as the fundamental). Three divisions vibrate three times as fast as the fundamental ; 4 at 4x fundamental, and so on. A tuning fork is made to vibrate at a single frequency. The way the harmonic vibrations combine to create sound is what makes it interesting and pleasant to the ear. Some harmonics interfere with others, producing a disonant sound, and this is important too because it keeps it from being just 'pretty'. Horns, vocal cords, etc. also vibrate in the same harmonic progression of equal divisions of the fundamental. their tones are different because of which harmonics are emphasized or muted.

Answer 3

when a guitar string vibrates, it actually vibrates in many different ways all put together.

firstly, the most dominant sound is that of the whole length of the string. in addition, there are countless other ways it can vibrate such as one where the vibration occurs around the midpoint of the string.

that is not the only two ways though, it can also vibrate around 2 points ( located at the "thirds" ) like a sine wave. there is also one where it vibrates around 3 points ( quarter lengths ) and etc. these are known as the "harmonic" vibrations and they give the characteristic rich sound of the vibrating string.

these smaller vibrations ( harmonics ) can only be heard when the main dominant first vibration is muted while allowing the rest of the string to vibrate around these "node" points ( thirds, quarters etc )

this is done by holding your finger lightly near the "node points" so that the string can only vibrate through that point.

the concept is best understood visually but unfortunately not possible here !

hope i shed some light on the topic though !

thanks :)