Acoustics of the hammered dulcimer
Canfield, Gregory H.
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The hammered dulcimer is a folk instrument of trapezoidal shape that is played with two hand-held hammers. For this thesis, the acoustics of two professionally made and two home-made hammered dulcimers were studied. Using the techniques of mode scanning, modal impact analysis, and time average holography, the modal frequencies and modal shapes of the dulcimers were determined. As would be expected by the different designs of the four instruments, the modal frequencies and shapes varied greatly between the dulcimers. In most modes, a nodal line occurs near the bridges. A (l,0)-mode of the soundboard was found in three of the instruments, and for the professionally made instruments, the soundboard brace divided the soundboard into two similarly sized regions and accentuated the (1,0) mode by having the brace near a nodal line. Although the asymmetries of the internal bracing and the lack of literature on orthotropic trapezoidal plates made it difficult to model the vibration of the soundboards, the backs of two of the dulcimers have been modeled either as orthotropic rectangular plates or as isotropic trapezoidal plates, and good agreement with the experimental results was obtained.