This paper examines a method used to quantify multiple damping types acting simultaneously on bronzewound guitar strings. This method involves curve-fitting the time-decay envelopes of filtered string harmonics and using the fitted damping parameters in a single-degree-of-freedom (SDOF) model to verify the results and potentially identify relevant damping design variables for frequency-based damping. Material, aerodynamic, and friction damping are considered in this study, and each type of damping was isolated by changing the environmental conditions. The damping forces from all three types of damping add linearly in the SDOF model, allowing the time decay envelope of each harmonic to be fitted with a function that is a linear summation of each decay function. Both the SDOF model and curve-fitting algorithm could not produce reliable damping coefficients due to summation effects of the three decay functions. It was found that the curve-fitting routine and model solution were most sensitive to the aerodynamic parameter because of the decay function’s ability to fit both a steep initial and flat steady-state decay. The test results from vacuum chamber data showed that friction damping comes primarily from the windings on the string rubbing against one another, and that material damping increases linearly with frequency and is proportional to the velocity. Empirically, this gives merit to viscous-like damping as a potential model for material damping.Full Text
Article published Jun 22, 2011.
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The Savart Journal is published in collaboration with the Guild of American Luthiers.
Jonathan Wesley Christian
Purdue University Alumni: BS in MET in 2008, MS in 2011
Faurecia- Emissions Control Technologies
Product Engineer - Noise and Vibration Harshness Group