This string trial was the first trial run using polyester thread, and was also the first successful twisted rope polyester guqin string I made. I decided to use the exact same parameters from the previous successful and optimized trial #13 string made from nylon, since nylon and polyester are so similar mechanically. To my surprise, even with the same thread diameter and count, the polyester string actually ended up noticeably thinner than its nylon counterpart which it was based off of. It turns out that for this thread, the polyester strands can be twisted tighter and closer together, resulting in a slightly thinner string as compared with nylon using the same diameter thread and thread count. Polyester has considerably less stretch, and is denser than nylon, resulting in a stiffer and brighter sounding string. It turned out that this string was a bit too thin for use as a guqin string #7, however I have found that it works perfectly as a tsugaru shamisen ni no ito (second string).
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 #14 PARAMETERS
Thread: Barbook’s Weaverbird Polyester #15 Brown
Thread Diameter (in.): 0.0048″
Theoretical Calculated Twisted Substrand Diameter (in.): 0.01590″
Theoretical Calculated Twisted Total Diameter (in.): 0.0343″
Thread Strength: 1.5lbs
# of Substrands: 3
# of Threads per Substrand: 8
Total Thread Count: 24
# of Primary Twists: 2325
Twist Angle (degrees): 41.2
Substrand Twist Direction: Clockwise
String Twist Direction: Clockwise
Primary Twisting Tension: 3lbs
Secondary Twisting Tension: 3lbs
Starting Length (in.): 120″
Ending Length (in.): n/a
STRING TRIAL #14 DATA
1. Linear Spectrum Harmonic Content Graphs
3. Spectrograms (Window 4096)
4. Spectrograms (Window 2048)
5. Spectrograms (Window 512)
- 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.
- 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.
- 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.
- 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.
- 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.