Nylon Guqin String Trial #5


This string is the second experimental qin string I successfully made and tested. After several tries with 4-ply twisted ropes, I found that 3-ply produced much smoother strings with this particular material and set of parameters. I also attempted to see what would happen if synthetic nylon strings were coated in glue. This glue was a non-toxic handmade dextrin based glue, in which the string was cooked in for a set period of time before stretching and drying, similar in method for traditional silk string making. The data below is for the string after the glue was applied. The glue seemed to deaden the tone of the string however, which is to be expected as the heavy glue adds extra linear mass to the length of the string, and the glue made was not optimized, and was my first attempt at making my own glue. After several more trials, I decided that for these particular strings, glue would not be needed, and in order to keep the rope structure from unraveling, the strings are tightly knotted at each end after further stretching and conditioning by hand. However, these experiments with glued synthetic strings helped me formulate further hypothesis on the workings of glue in tone production of strings, which may play a significant role with silk strings.

Included in this page are all of the major string parameters that I have obtained so far for this string, as well as all relevant data I have collected and analyzed for this string, including harmonic content data, spectrograms, and autocorrelation graphs. You can enlarge the images by clicking on the thumbnails.


STRING TRIAL #5 PARAMETERS

Material: Nylon

Thread: Middleburg Thread #15 Nylon Beige

Thread Diameter (in.): 0.0048″

Theoretical Calculated Twisted Substrand Diameter (in.): 0.01415″

Theoretical Calculated Twisted Total Diameter (in.): 0.0305″

Thread Strength: 2lbs

# of Substrands: 3

# of Threads per Substrand: 6

Total Thread Count: 18

# of Primary Twists: 2400

Twist Angle (degrees): 32.5

Substrand Twist Direction: Clockwise

String Twist Direction: Clockwise

Primary Twisting Tension: 2lbs

Secondary Twisting Tension: 2lbs

Starting Length (in.): 120″

Ending Length (in.): 103.5″

String Coating: Homemade Dextrin Based Glue


STRING TRIAL #5 DATA

1. Linear Spectrum Harmonic Content Graphs

 

2. Autocorrelation

 

3. Spectrograms (Window 4096)

 

4. Spectrograms (Window 2048)

 

5. Spectrograms (Window 512)


STRING TRIAL #5 DATA DESCRIPTIONS

  1. Linear Spectrum Harmonic Content Graphs – Shows the harmonic content of each string, graphed along the linear spectrum in terms of frequency to intensity. A very accurate way to easily visualize the harmonics and overtones of each string.
  2. Autocorrelation – Shows the periodic nature or trends from a given set of data. Autocorrelation can provide a unique look at data, and can reveal repeating patterns from seemingly random datapoints. For this application, it is derived from the original signal and more clearly shows the decaying oscillatory nature of the plucked string.
  3. Spectrograms (Window 4096) – Shows the spectrogram of each string, with a window setting of 4096. This setting allows one to clearly view all of the harmonics by showing the frequency, intensity, and duration of each harmonic. This graph can be most easily cross-correlated to the linear spectrum harmonic content graphs to compare durations and intensities of harmonics in a string.
  4. Spectrograms (Window 2048) –  Shows the spectrogram of each string, with a window setting of 2048. For this application, I have found that this setting is ideal in viewing the oscillatory instabilities of the guqin string more clearly, which cannot be seen as well in higher window settings. These are seen as wavering lines, which are most noticeably present in the mid-upper harmonics.
  5. Spectrograms (Window 512) – Shows the spectrogram of each string, with a window setting of 512. For this application, I have found that this setting, while having the lowest frequency band resolution of the three settings, allows one to zoom out on the entirety of the harmonic spectrum, and see how the overall power level and intensity shifts from one string to another, and where the harmonic content is overall most present for a given string.