Measuring the Frequency Response Function of X-braced Guitar Top and Guitar
Abstract: In this study,
we measured the frequency response of an X-braced guitar top board and a fully
constructed guitar. The top was fixed on an aluminum rig and excited by an impact
hammer. A microphone recorded the radiated sound. Our Labview VIs analyzed the spectrums
of both the input and output signal. Then we evaluated the frequency response from these
two spectrums. The fundamental ... read moreresonance of the fully braced guitar top board is about
173 Hz. We also measured the effect of this bracing pattern, which could potentially
suppress lower modes and even the response at higher frequencies. The result from
measuring the guitar top does not show strong agreement with theoretical calculations. A
major reason might be the non-uniform boundary condition applied. We also tested a
fully-constructed guitar with the same top bracing configuration to investigate the
effects of the guitar body. The influence of the soundhole, back, and string tension was
also measured. The most significant effect of the body was that it significantly boosted
the response at lower frequencies and an additional breathing mode also appeared in the
spectrum. Data for measuring the fully constructed guitar has good agreement with past
studies, where the two distinct responses were captured around 100 Hz (soundhole mode)
and 200 Hz (plate mode). We tested the effect of the soundhole by covering it with the
cardboard, which dramatically reduced the response of the breathing mode, and the plate
response also shifted to lower frequencies. We added clay tablets on the back plate to
investigate its effect on the guitar frequency response. This led the breathing mode to
shift to lower frequencies. This shift had its maximum value when the additional weight
concentrated on the center of the back plate. The guitar was also tested without string
tensions, which results in a slight change in fundamental plate
Thesis (M.S.)--Tufts University, 2016.
Submitted to the Dept. of Mechanical Engineering.
Advisor: Chris Rogers.
Committee: Robert White, and Paul Lehrman.
Keyword: Acoustics.read less