title: The evolution of air resonance power efficiency in the violin and its ancestors.
abstract: The fact that acoustic radiation from a violin at air-cavity resonance is monopolar and can be determined by pure volume change is used to help explain related aspects of violin design evolution. By determining the acoustic conductance of arbitrarily shaped sound holes, it is found that air flow at the perimeter rather than the broader sound-hole area dominates acoustic conductance, and coupling between compressible air within the violin and its elastic structure lowers the Helmholtz resonance frequency from that found for a corresponding rigid instrument by roughly a semitone. As a result of the former, it is found that as sound-hole geometry of the violin's ancestors slowly evolved over centuries from simple circles to complex f-holes, the ratio of inefficient, acoustically inactive to total sound-hole area was decimated, roughly doubling air-resonance power efficiency. F-hole length then slowly increased by roughly 30% across two centuries in the renowned workshops of Amati, Stradivari and Guarneri, favouring instruments with higher air-resonance power, through a corresponding power increase of roughly 60%. By evolution-rate analysis, these changes are found to be consistent with mutations arising within the range of accidental replication fluctuations from craftsmanship limitations with subsequent selection favouring instruments with higher air-resonance power.
authors: Department of Mechanical Engineering , Massachusetts Institute of Technology, 77 Massachusetts Avenue , Cambridge, MA 02139, USA.
authors: Hadi T
authors: 0000-0003-1970-9901
authors: HT
authors: Nia
authors: Department of Mechanical Engineering , Massachusetts Institute of Technology, 77 Massachusetts Avenue , Cambridge, MA 02139, USA.
authors: Ankita D
authors: AD
authors: Jain
authors: Department of Mechanical Engineering , Massachusetts Institute of Technology, 77 Massachusetts Avenue , Cambridge, MA 02139, USA.
authors: Yuming
authors: Y
authors: Liu
authors: Department of Mechanical Engineering , Massachusetts Institute of Technology, 77 Massachusetts Avenue , Cambridge, MA 02139, USA.
authors: Mohammad-Reza
authors: MR
authors: Alam
authors: Violin Making, North Bennet St. School , 39 North Bennet St. , Boston, MA 02113, USA.
authors: Roman
authors: R
authors: Barnas
authors: Department of Mechanical Engineering , Massachusetts Institute of Technology, 77 Massachusetts Avenue , Cambridge, MA 02139, USA.
authors: Nicholas C
authors: NC
authors: Makris
keywords: Helmholtz resonance; f-hole; musical acoustics; sound hole evolution; violin acoustics; violin evolution