DRAFT: This module has unpublished changes.
Acoustic Guitar Harmonics

               The acoustic guitar is a very versatile instrument. It can be used to play resonant chords or twangy melodies. In my instrument analysis, I recorded and analyzed the vibrations of my Fender Starcaster Acoustic Guitar. Since it can be difficult to analyze many notes playing at the same time, I focused on 3 different harmonic notes played on the lowest string on the guitar. When a guitar string is plucked, a mixture of many tones is heard. However, the main note we hear is called the fundamental frequency, which is produced by the vibration of the whole length of a string. When one rests their finger lightly on the string at specific locations, then the fundamental frequency is muted, and one can hear the other notes vibrating when the string is struck. These notes are called harmonics.
              Harmonic notes can be used to add variety to melodies or to play notes that cannot be fretted on the guitar. They can also be very versatile when played on an electric guitar. Although harmonic notes are not as loud or resonant as the fundamental frequency, they can be quite prominent.  The harmonic frequency produced by touching the midpoint of the string produces the most prominent harmonic note which is an octave higher than the fundamental frequency. The second most prominent harmonic note is the fifth above the octave decribed previously, this is sounded by touching the string above the 7th or 19th fret(this splits the string into thirds). The third most prominent harmonic note is the two-octaves higher note produced by splitting the string into fourths, for this analysis I used the spot above the fifth fret. 
               The following is a recording of the three harmonic notes on my acoustic guitar. Starting at 0:05 on the recording, I am playing the E4 harmonic note on the lowest (E2) string with my finger lightly touching the string over the fifth fret. The second note is a B3 played by touching the low E string over the seventh fret. The third note is an E3, which is played by touching the lowest string over the twelfth fret. I repeat these notes in that respective order several more times in the recording.
DRAFT: This module has unpublished changes.
DRAFT: This module has unpublished changes.

                 I chose to analyze the harmonics on the open A string since it seemed to have the loudest and clearest harmonic notes, which makes it easier to interpret the readings from Soundcard Oscilloscope. The following is a picture of the open A2 string oscilloscope reading. The second picture is the oscilloscope reading of the A3 harmonic note.

 

Oscilloscope: A2 open string

 

Oscilloscope: A3 Harmonic(12th fret A2 string)

 

 

A single note/frequency is seen as a perfect sinusoid wave in the oscilloscope. When there are many notes playing at once the oscilloscope shows a distored wave pattern. As you can see on the first oscilloscope graph, the open A string has lost much of its sinusoid-like wave, and is quite distorted, suggesting there are several notes playing at once. The second graph showing the A3 harmonic is much clearer, and is not as distorted as the open A, suggesting that there are likely less vibrations in the air.

 

The following pictures are graphs from the spectrum analyzer, which graphs the amplitude vs the frequency of the vibrations in the air. The first picture shows the different frequencies of the vibrations produced by plucking the open A2 string. The second picture shows the frequencies of the vibrations produced by plucking the A3 harmonic note on the 12th fret of the A2 string.

 

Spectrum Analyzer: Open A2 String

Spectrum Analyzer: A3 Harmonic(12th fret A2 string)

 

As you can see, the harmonic note is much more focused on one frequency when compared to the open string, which has many different frequencies being heard at once(with the most prominent hill being the fundamental note). There are less frequencies in the harmonic note because they are being muted out by my finger. These spectrum analyzer graphs agree with the findings from the oscilloscope graphs, since they both support the idea that there are many more frequencies being produced by the open A2 string than in the A3 harmonic note. 

 

DRAFT: This module has unpublished changes.