Effects of peg systems on structural vibration and acoustic response in an oud

Abstract

Peg systems form part of the mechanical structure of a stringed instrument, but their contribution to the oud’s response has received limited experimental attention. This exploratory pilot study compared four conditions on one unstrung oud: No Pegs, Rosewood Pegs, Ebony Pegs, and Wittner Mechanical Pegs. Impact-based frequency-response measurements combined bridge and neck–pegbox vibration with force-normalized acoustic response. Three resonance regions selected by qualitative screening of the broadband spectra, labelled Mode 1–Mode 3 for this comparison, were tracked at a frequency increment of 1.5625 Hz. Of these three regions, Mode 3 showed the largest frequency shifts. Relative to No Pegs, the Wittner condition shifted the bridge peak downward by 10.94 Hz and increased the bridge, neck–pegbox, and acoustic peak levels by 2.51, 11.18, and 5.39 dB, respectively. Mode 2 showed contrasting bridge and neck responses, while acoustic changes were not consistently monotonic across conditions. At the evaluated frequencies, coherence was high for the No Pegs neck and Ebony bridge records and lower for the No Pegs and Rosewood acoustic records; no acoustic coherence was recorded for Ebony or Wittner. The results identify mode-dependent changes associated with peg-system substitution and support examining the pegbox within the coupled body–neck structure. This single-instrument comparison does not isolate mass from other mechanical differences or establish tonal superiority under playing conditions.