The link between sound and guitars

In this final blog, I want to touch on how sound is linked to guitars. On the previous blog, my research was based on how an electric guitar produces its sounds but now, I am going to share about acoustic guitars.

Similarly, the sounds produce by an acoustic guitar follows the same principles of the link between amplitude and volume, and the link between frequency and pitch.

The structural engineering of a guitar is indeed very unique. Although just made of wood and strings with high tensions, the guitar has managed to produce different sounds of different frequencies. There are normally 2 types of materials the strings are made if, making the sound very crucial, they are the nylon and metal (e.g steel).

This is the nylon string guitar having a softer touch effect and generally a softer sound.

These are the metal strings guitar that are generally louder because of the more vibrations it can produce.

But overall, the main factor that allows these sounds from the acoustic guitar comes from the wood and air hole. Imagine pulling a rubber band, there is hardly any sound, this applies the same to a guitar. The sound that we hear actually comes from the vibration of particles from the wood and air space, passing on its energy into our ears. There are many different type of woods that guitars are made of and some examples are mahogany, maple, rosewood and oak, moreover all of them giving a unique tone. 

This graph shows the sounds produce by the guitar in terms of time. It is very clear that the guitar does not give out perfect pitch sounds like an oscilloscope and this is the reason for its unique tones.   

Generally the pitch of the guitar depend of certain things.

1) The mass of strings

2) The tension of the strings

3) Free space of the strings

4) The vibration of the strings

The final thing I would like to write about is the sound linkage and frequency. 

Theses are all the notes of 1 octave in a guitar fret board. Each fret that a player presses on, produces a frequency that results in all these different pitches.

Generally, the sound of a guitar follows the physics formula of Frequency=Speed/Wavelength.
That is why when a guitarist moves up the fret board, the pitch gets higher because the shorter the wavelength, the higher its frequency. The thicker the string, the slower it moves,explaining why the thicker ones produce a smaller frequency,giving a smaller frequency.

The 2 ends show the whole wavelength of guitar. 

As we follow a certain formula, we can calculate what pitch the guitar would give when we press of a fraction of the whole fret board.

scale position touched	fraction of string length
octave	1/2
fifth	1/3
fourth	1/4
major third	1/5
minor third	1/6
augmented fourth	2/7
minor sixth	3/8
major second	1/9

This is the general formula which guitarists use. For example, if the guitar has 24 frets, and you press on the 12 fret, it would give you the same note but one octave higher. This sequence is indeed a complicated series which requires a proficient musical knowledge such as the major second of a C being a D etc.

To conclude, there is more to a guitar then I have just mention. There are more complicated formulas and information which goes into a very high level of physics. These blogs has indeed help me to understand that there is a science behind the instrument I play.

Thank You
Elijah Wong

Sources:
http://newt.phys.unsw.edu.au/~jw/guitarintro.html
http://newt.phys.unsw.edu.au/jw/strings.html
http://ideastations.org/science-matters/sites-and-wonders/guitars-sounds-and-science
http://www.businessinsider.my/physics-guitar-mystery-oxford-rockstar-rock-music-2014-9/#JMCgmKZtilT2lxdJ.97
http://www.premierguitar.com/articles/The_Science_of_Tone
http://www.soundonsound.com/sos/may02/articles/cholakis.asp
https://www.google.com/search?q=guitar+fretboard&espv=2&biw=1366&bih=623&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMIvNGEvbyKxwIVSFCOCh1xJgwY#imgrc=6UoVO0hJrvsbwM%3A